Changes for page 12 Validation and Transformation Language (VTL)

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	1	+Artefact\|Attribute\|Code\|Code list\|Component\|Concept scheme\|Currency\|Data set\|Data structure definition\|Dataflow\|Dimension\|Facet\|Maintainable artefact\|Measure\|Nameable artefact\|Representation\|SDMX Information Model\|Statistical data and metadata exchange\|Structural metadata\|Validation and transformation language

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  == 12.1 Introduction ==
--The Validation and Transformation Language (VTL) supports the definition of Transformations, which are algorithms to calculate new data starting from already existing ones{{footnote}}The Validation and Transformation Language is a standard language designed and published under the SDMX initiative. VTL is described in the VTL User and Reference Guides available on the SDMX website https://sdmx.org.{{/footnote}}. The purpose of the VTL in the SDMX context is to enable the:
++The [[Validation and Transformation Language>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] ([[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]) supports the definition of Transformations, which are algorithms to calculate new data starting from already existing ones{{footnote}}The Validation and Transformation Language is a standard language designed and published under the SDMX initiative. VTL is described in the VTL User and Reference Guides available on the SDMX website https://sdmx.org.{{/footnote}}. The purpose of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] context is to enable the:
  * definition of validation and transformation algorithms, in order to specify how to calculate new data from existing ones;
--* exchange of the definition of VTL algorithms, also together the definition of the data structures of the involved data (for example, exchange the data structures of a reporting framework together with the validation rules to be applied, exchange the input and output data structures of a calculation task together with the VTL Transformations describing the calculation algorithms);
--* compilation and execution of VTL algorithms, either interpreting the VTL Transformations or translating them in whatever other computer language is deemed as appropriate.
++* exchange of the definition of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] algorithms, also together the definition of the data structures of the involved data (for example, exchange the data structures of a reporting framework together with the validation rules to be applied, exchange the input and output data structures of a calculation task together with the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations describing the calculation algorithms);
++* compilation and execution of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] algorithms, either interpreting the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations or translating them in whatever other computer language is deemed as appropriate.
--It is important to note that the VTL has its own information model (IM), derived from the Generic Statistical Information Model (GSIM) and described in the VTL User Guide. The VTL IM is designed to be compatible with more standards, like SDMX, DDI (Data Documentation Initiative) and GSIM, and includes the model artefacts that can be manipulated (inputs and/or outputs of Transformations, e.g. "Data Set", "Data Structure") and the model artefacts that allow the definition of the transformation algorithms (e.g. "Transformation", "Transformation Scheme").
++It is important to note that the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] has its own information model (IM), derived from the Generic Statistical Information Model (GSIM) and described in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] User Guide. The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] IM is designed to be compatible with more standards, like [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], DDI (Data Documentation Initiative) and GSIM, and includes the model [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] that can be manipulated (inputs and/or outputs of Transformations, e.g. "[[Data Set>>doc:sdmx:Glossary.Data set.WebHome]]", "Data Structure") and the model [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] that allow the definition of the transformation algorithms (e.g. "Transformation", "Transformation Scheme").
--The VTL language can be applied to SDMX artefacts by mapping the SDMX IM model artefacts to the model artefacts that VTL can manipulate{{footnote}}In this chapter, in order to distinguish VTL and SDMX model artefacts, the VTL ones are written in the Arial font while the SDMX ones in Courier New.{{/footnote}}. Thus, the SDMX artefacts can be used in VTL as inputs and/or outputs of Transformations. It is important to be aware that the artefacts do not always have the same names in the SDMX and VTL IMs, nor do they always have the same meaning. The more evident example is given by the SDMX Dataset and the VTL "Data Set", which do not correspond one another: as a matter of fact, the VTL "Data Set" maps to the SDMX "Dataflow", while the SDMX "Dataset" has no explicit mapping to VTL (such an abstraction is not needed in the definition of VTL Transformations). A SDMX "Dataset", however, is an instance of a SDMX "Dataflow" and can be the artefact on which the VTL transformations are executed (i.e., the Transformations are defined on Dataflows and are applied to Dataflow instances that can be Datasets).
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] language can be applied to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] by (% style="color:#e74c3c" %)mapping(%%) the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] IM model [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] to the model [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] that [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] can manipulate{{footnote}}In this chapter, in order to distinguish VTL and SDMX model artefacts, the VTL ones are written in the Arial font while the SDMX ones in Courier New.{{/footnote}}. Thus, the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] can be used in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] as inputs and/or outputs of Transformations. It is important to be aware that the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] do not always have the same names in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] and [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] IMs, nor do they always have the same meaning. The more evident example is given by the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataset>>doc:sdmx:Glossary.Data set.WebHome]] and the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] "[[Data Set>>doc:sdmx:Glossary.Data set.WebHome]]", which do not correspond one another: as a matter of fact, the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] "[[Data Set>>doc:sdmx:Glossary.Data set.WebHome]]" (% style="color:#e74c3c" %)maps(%%) to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] "[[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]]", while the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] "[[Dataset>>doc:sdmx:Glossary.Data set.WebHome]]" has no explicit (% style="color:#e74c3c" %)mapping(%%) to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (such an abstraction is not needed in the definition of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations). A [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] "[[Dataset>>doc:sdmx:Glossary.Data set.WebHome]]", however, is an instance of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] "[[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]]" and can be the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] on which the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] transformations are executed (i.e., the Transformations are defined on [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]] and are applied to [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] instances that can be Datasets).
--The VTL programs (Transformation Schemes) are represented in SDMX through the TransformationScheme maintainable class which is composed of Transformation (nameable artefact). Each Transformation assigns the outcome of the evaluation of a VTL expression to a result.
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] programs (Transformation Schemes) are represented in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] through the TransformationScheme maintainable class which is composed of Transformation ([[nameable artefact>>doc:sdmx:Glossary.Nameable artefact.WebHome]]). Each Transformation assigns the outcome of the evaluation of a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] expression to a result.
--This section does not explain the VTL language or any of the content published in the VTL guides. Rather, this is a description of how the VTL can be used in the SDMX context and applied to SDMX artefacts.
++This section does not explain the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] language or any of the content published in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] guides. Rather, this is a description of how the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] can be used in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] context and applied to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]].
--== 12.2  References to SDMX artefacts from VTL statements ==
++== 12.2 References to SDMX artefacts from VTL statements ==
  === 12.2.1 Introduction ===
--The VTL can manipulate SDMX artefacts (or objects) by referencing them through predefined conventional names (aliases).
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] can manipulate [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] (or objects) by referencing them through predefined conventional names (aliases).
--The alias of an SDMX artefact can be its URN (Universal Resource Name), an abbreviation of its URN or another user-defined name.
++The alias of an [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] can be its URN (Universal Resource Name), an abbreviation of its URN or another user-defined name.
--In any case, the aliases used in the VTL Transformations have to be mapped to the SDMX artefacts through the VtlMappingScheme and VtlMapping classes (see the section of the SDMX IM relevant to the VTL). A VtlMapping allows specifying the aliases to be used in the VTL Transformations, Rulesets{{footnote}}See also the section "VTL-DL Rulesets" in the VTL Reference Manual.{{/footnote}} or User Defined Operators{{footnote}}The VTLMappings are used also for User Defined Operators (UDO). Although UDOs are envisaged to be defined on generic operands, so that the specific artefacts to be manipulated are passed as parameters at their invocation, it is also possible that an UDO invokes directly some specific SDMX artefacts. These SDMX artefacts have to be mapped to the corresponding aliases used in the definition of the UDO through the VtlMappingScheme and VtlMapping classes as well.{{/footnote}} to reference SDMX artefacts. A VtlMappingScheme is a container for zero or more VtlMapping.
++In any case, the aliases used in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations have to be (% style="color:#e74c3c" %)mapped(%%) to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] through the VtlMappingScheme and VtlMapping classes (see the section of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] IM relevant to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]). A VtlMapping allows specifying the aliases to be used in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations, Rulesets{{footnote}}See also the section "VTL-DL Rulesets" in the VTL Reference Manual.{{/footnote}} or User Defined Operators{{footnote}}The VTLMappings are used also for User Defined Operators (UDO). Although UDOs are envisaged to be defined on generic operands, so that the specific artefacts to be manipulated are passed as parameters at their invocation, it is also possible that an UDO invokes directly some specific SDMX artefacts. These SDMX artefacts have to be mapped to the corresponding aliases used in the definition of the UDO through the VtlMappingScheme and VtlMapping classes as well.{{/footnote}} to reference [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]]. A VtlMappingScheme is a container for zero or more VtlMapping.
--The correspondence between an alias and a SDMX artefact must be one-to-one, meaning that a generic alias identifies one and just one SDMX artefact while a SDMX artefact is identified by one and just one alias. In other words, within a VtlMappingScheme an artefact can have just one alias and different artefacts cannot have the same alias.
++The correspondence between an alias and a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] must be one-to-one, meaning that a generic alias identifies one and just one [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] while a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is identified by one and just one alias. In other words, within a VtlMappingScheme an [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] can have just one alias and different [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] cannot have the same alias.
  The references through the URN and the abbreviated URN are described in the following paragraphs.
  === 12.2.2 References through the URN ===
--This approach has the advantage that in the VTL code the URN of the referenced artefacts is directly intelligible by a human reader but has the drawback that the references are verbose.
++This approach has the advantage that in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] code the URN of the referenced [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] is directly intelligible by a human reader but has the drawback that the references are verbose.
--The SDMX URN{{footnote}}For a complete description of the structure of the URN see the SDMX 2.1 Standards - Section 5 - Registry Specifications, paragraph 6.2.2 ("Universal Resource Name (URN)").{{/footnote}}(% style="font-size:12px" %) (%%)is the concatenation of the following parts, separated by special symbols like dot, equal, asterisk, comma, and parenthesis:
++The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] URN{{footnote}}For a complete description of the structure of the URN see the SDMX 2.1 Standards - Section 5 - Registry Specifications, paragraph 6.2.2 ("Universal Resource Name (URN)").{{/footnote}}(% style="font-size:12px" %) (%%)is the concatenation of the following parts, separated by special symbols like dot, equal, asterisk, comma, and parenthesis:
  * SDMXprefix
--* SDMX-IM-package-name
++* [[SDMX-IM>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]-package-name
  * class-name
  * agency-id
  * maintainedobject-id
--* maintainedobject-version
++* maintainedobject-(% style="color:#e74c3c" %)version
  * container-object-id{{footnote}}The container-object-id can repeat and may not be present.{{/footnote}}
  * object-id
  The generic structure of the URN is the following:
--SDMXprefix.SDMX-IM-package-name.class-name=agency-id:maintainedobject-id (maintainedobject-version).*container-object-id.object-id
++SDMXprefix.[[SDMX-IM>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]-package-name.class-name=agency-id:maintainedobject-id (maintainedobject-(% style="color:#e74c3c" %)version(%%)).*container-object-id.object-id
--The **SDMXprefix** is "urn:sdmx:org", always the same for all SDMX artefacts.
++The **SDMXprefix** is "urn:[[sdmx>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]:org", always the same for all [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]].
--The SDMX-IM-package-name** **is the concatenation of the string** **"sdmx.infomodel." with the package-name, which the artefact belongs to. For example, for referencing a Dataflow the SDMX-IM-package-name is "sdmx.infomodel.datastructure", because the class Dataflow belongs to the package "datastructure".
++The [[SDMX-IM>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]-package-name** **is the concatenation of the string** **"[[sdmx>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]].infomodel." with the package-name, which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] belongs to. For example, for referencing a [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] the [[SDMX-IM>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]-package-name is "[[sdmx>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]].infomodel.datastructure", because the class [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] belongs to the package "datastructure".
--The class-name is the name of the SDMX object class, which the SDMX object belongs to (e.g., for referencing a Dataflow the class-name is "Dataflow"). The VTL can reference SDMX artefacts that belong to the classes Dataflow, Dimension, TimeDimension, Measure, DataAttribute, Concept, Codelist.
++The class-name is the name of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] object class, which the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] object belongs to (e.g., for referencing a [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] the class-name is "[[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]]"). The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] can reference [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] that belong to the classes [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], TimeDimension, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]], DataAttribute, (% style="color:#e74c3c" %)Concept(%%), Codelist.
--The agency-id is the acronym of the agency that owns the definition of the artefact, for example for the Eurostat artefacts the agency-id is "ESTAT"). The agency-id can be composite (for example AgencyA.Dept1.Unit2).
++The agency-id is the acronym of the agency that owns the definition of the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]], for example for the Eurostat [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] the agency-id is "ESTAT"). The agency-id can be composite (for example AgencyA.Dept1.Unit2).
--The maintainedobject-id is the name of the maintained object which the artefact belongs to, and in case the artefact itself is maintainable{{footnote}}i.e., the artefact belongs to a maintainable class{{/footnote}}, coincides with the name of the artefact. Therefore the maintainedobject-id depends on the class of the artefact:
++The maintainedobject-id is the name of the maintained object which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] belongs to, and in case the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] itself is maintainable{{footnote}}i.e., the artefact belongs to a maintainable class{{/footnote}}, coincides with the name of the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]]. Therefore the maintainedobject-id depends on the class of the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]]:
--* if the artefact is a Dataflow, which is a maintainable class, the maintainedobject-id is the Dataflow name (dataflow-id);
--* if the artefact is a Dimension, Measure, TimeDimension or DataAttribute, which are not maintainable and belong to the
++* if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], which is a maintainable class, the maintainedobject-id is the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] name ([[dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]]-id);
++* if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], [[Measure>>doc:sdmx:Glossary.Measure.WebHome]], TimeDimension or DataAttribute, which are not maintainable and belong to the
--DataStructure maintainable class, the maintainedobject-id is the name of the DataStructure (dataStructure-id) which the artefact belongs to;
++DataStructure maintainable class, the maintainedobject-id is the name of the DataStructure (dataStructure-id) which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] belongs to;
--* if the artefact is a Concept, which is not maintainable and belongs to the ConceptScheme maintainable class, the maintainedobject-id is the name of the ConceptScheme (conceptScheme-id) which the artefact belongs to;
--* if the artefact is a Codelist, which is a maintainable class, the maintainedobject-id is the Codelist name (codelist-id).
++* if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a (% style="color:#e74c3c" %)Concept(%%), which is not maintainable and belongs to the ConceptScheme maintainable class, the maintainedobject-id is the name of the ConceptScheme (conceptScheme-id) which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] belongs to;
++* if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a Codelist, which is a maintainable class, the maintainedobject-id is the Codelist name (codelist-id).
--The maintainedobject-version is the version, according to the SDMX versioning rules, of the maintained object which the artefact belongs to (for example, possible versions might be 1.0, 2.3, 1.0.0, 2.1.0 or 3.1.2).
++The maintainedobject-(% style="color:#e74c3c" %)version(%%) is the (% style="color:#e74c3c" %)version(%%), according to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] versioning rules, of the maintained object which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] belongs to (for example, possible (% style="color:#e74c3c" %)versions(%%) might be 1.0, 2.3, 1.0.0, 2.1.0 or 3.1.2).
--The container-object-id does not apply to the classes that can be referenced in VTL Transformations, therefore is not present in their URN.
++The container-object-id does not apply to the classes that can be referenced in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations, therefore is not present in their URN.
--The object-id is the name of the non-maintainable artefact (when the artefact is maintainable its name is already specified as the maintainedobject-id, see above), in particular it has to be specified:
++The object-id is the name of the non-[[maintainable artefact>>doc:sdmx:Glossary.Maintainable artefact.WebHome]] (when the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is maintainable its name is already specified as the maintainedobject-id, see above), in particular it has to be specified:
--* if the artefact is a Dimension, TimeDimension, Measure or DataAttribute (the object-id is the name of one of the artefacts above, which are data structure components)
--* if the artefact is a Concept (the object-id is the name of the Concept)
++* if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], TimeDimension, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] or DataAttribute (the object-id is the name of one of the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] above, which are data structure components)
++* if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a (% style="color:#e74c3c" %)Concept(%%) (the object-id is the name of the (% style="color:#e74c3c" %)Concept(%%))
--For example, by using the URN, the VTL Transformation that sums two SDMX Dataflows DF1 and DF2 and assigns the result to a third persistent Dataflow DFR, assuming that DF1, DF2 and DFR are the maintainedobject-id of the three Dataflows, that their version is 1.0.0 and their Agency is AG, would be written as{{footnote}}Since these references to SDMX objects include non-permitted characters as per the VTL ID notation, they need to be included between single quotes, according to the VTL rules for irregular names.{{/footnote}}:
++For example, by using the URN, the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformation that sums two [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]] DF1 and DF2 and assigns the result to a third persistent [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DFR, assuming that DF1, DF2 and DFR are the maintainedobject-id of the three [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]], that their (% style="color:#e74c3c" %)version(%%) is 1.0.0 and their Agency is AG, would be written as
++{{footnote}}Since these references to SDMX objects include non-permitted characters as per the VTL ID notation, they need to be included between single quotes, according to the VTL rules for irregular names.{{/footnote}}:
++
  > 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' <-
  > 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
  > 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
@@ -86,25 +86,25 @@
  === 12.2.3 Abbreviation of the URN ===
--The complete formulation of the URN described above is exhaustive but verbose, even for very simple statements. In order to reduce the verbosity through a simplified identifier and make the work of transformation definers easier, proper abbreviations of the URN are possible. Using this approach, the referenced artefacts remain intelligible in the VTL code by a human reader.
++The complete formulation of the URN described above is exhaustive but verbose, even for very simple statements. In order to reduce the verbosity through a simplified identifier and make the work of transformation definers easier, proper abbreviations of the URN are possible. Using this approach, the referenced [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] remain intelligible in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] code by a human reader.
--The URN can be abbreviated by omitting the parts that are not essential for the identification of the artefact or that can be deduced from other available information, including the context in which the invocation is made. The possible abbreviations are described below.
++The URN can be abbreviated by omitting the parts that are not essential for the identification of the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] or that can be deduced from other available information, including the context in which the invocation is made. The possible abbreviations are described below.
--* The SDMXprefix can be omitted for all the SDMX objects, because it is a prefixed string (urn:sdmx:org), always the same for SDMX objects.
--* The SDMX-IM-package-name** **can be omitted as well because it can be deduced from the class-name that follows it (the table of the SDMX-IM packages and classes that allows this deduction is in the SDMX 2.1 Standards - Section 5 - Registry Specifications, paragraph 6.2.3). In particular, considering the object classes of the artefacts that VTL can reference, the package is:
--** "datastructure" for the classes Dataflow, Dimension, TimeDimension, Measure, DataAttribute,
--** "conceptscheme" for the class Concept,
++* The SDMXprefix can be omitted for all the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] objects, because it is a prefixed string (urn:[[sdmx>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]:org), always the same for [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] objects.
++* The [[SDMX-IM>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]-package-name** **can be omitted as well because it can be deduced from the class-name that follows it (the table of the [[SDMX-IM>>doc:sdmx:Glossary.SDMX Information Model.WebHome]] packages and classes that allows this deduction is in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 Standards - Section 5 - Registry Specifications, paragraph 6.2.3). In particular, considering the object classes of the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] that [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] can reference, the package is:
++** "datastructure" for the classes [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], TimeDimension, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]], DataAttribute,
++** "conceptscheme" for the class (% style="color:#e74c3c" %)Concept(%%),
  ** "codelist" for the class Codelist.
--* The class-name can be omitted as it can be deduced from the VTL invocation. In particular, starting from the VTL class of the invoked artefact (e.g. dataset, component, identifier, measure, attribute, variable, valuedomain), which is known given the syntax of the invoking VTL operator{{footnote}}For the syntax of the VTL operators see the VTL Reference Manual{{/footnote}}, the SDMX class can be deduced from the mapping rules between VTL and SDMX (see the section "Mapping between VTL and SDMX" hereinafter){{footnote}}In case the invoked artefact is a VTL component, which can be invoked only within the invocation of a VTL data set (SDMX Dataflow), the specific SDMX class-name (e.g. Dimension, TimeDimension, Measure or DataAttribute) can be deduced from the data structure of the SDMX Dataflow, which the component belongs to.{{/footnote}}.
--* If the agency-id is not specified, it is assumed by default equal to the agency-id of the TransformationScheme, UserDefinedOperatorScheme or RulesetScheme from which the artefact is invoked. For example, the agencyid can be omitted if it is the same as the invoking TransformationScheme and cannot be omitted if the artefact comes from another agency{{footnote}}If the Agency is composite (for example AgencyA.Dept1.Unit2), the agency is considered different even if only part of the composite name is different (for example AgencyA.Dept1.Unit3 is a different Agency than the previous one). Moreover the agency-id cannot be omitted in part (i.e., if a TransformationScheme owned by AgencyA.Dept1.Unit2 references an artefact coming from AgencyA.Dept1.Unit3, the specification of the agency-id becomes mandatory and must be complete, without omitting the possibly equal parts like AgencyA.Dept1){{/footnote}}. Take also into account that, according to the VTL consistency rules, the agency of the result of a Transformation must be the same as its TransformationScheme, therefore the agency-id can be omitted for all the results (left part of Transformation statements).
++* The class-name can be omitted as it can be deduced from the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] invocation. In particular, starting from the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] class of the invoked [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] (e.g. [[dataset>>doc:sdmx:Glossary.Data set.WebHome]], [[component>>doc:sdmx:Glossary.Component.WebHome]], identifier, [[measure>>doc:sdmx:Glossary.Measure.WebHome]], [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]], variable, valuedomain), which is known given the syntax of the invoking [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operator{{footnote}}For the syntax of the VTL operators see the VTL Reference Manual{{/footnote}}, the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] class can be deduced from the mapping rules between [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (see the section "Mapping between [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]" hereinafter){{footnote}}In case the invoked artefact is a VTL component, which can be invoked only within the invocation of a VTL data set (SDMX Dataflow), the specific SDMX class-name (e.g. Dimension, TimeDimension, Measure or DataAttribute) can be deduced from the data structure of the SDMX Dataflow, which the component belongs to.{{/footnote}}.
++* If the agency-id is not specified, it is assumed by default equal to the agency-id of the TransformationScheme, UserDefinedOperatorScheme or RulesetScheme from which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is invoked. For example, the agencyid can be omitted if it is the same as the invoking TransformationScheme and cannot be omitted if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] comes from another agency{{footnote}}If the Agency is composite (for example AgencyA.Dept1.Unit2), the agency is considered different even if only part of the composite name is different (for example AgencyA.Dept1.Unit3 is a different Agency than the previous one). Moreover the agency-id cannot be omitted in part (i.e., if a TransformationScheme owned by AgencyA.Dept1.Unit2 references an artefact coming from AgencyA.Dept1.Unit3, the specification of the agency-id becomes mandatory and must be complete, without omitting the possibly equal parts like AgencyA.Dept1){{/footnote}}. Take also into account that, according to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] consistency rules, the agency of the result of a Transformation must be the same as its TransformationScheme, therefore the agency-id can be omitted for all the results (left part of Transformation statements).
  * As for the maintainedobject-id, this is essential in some cases while in other cases it can be omitted:
--** if the referenced artefact is a Dataflow, which is a maintainable class, the maintainedobject-id is the dataflow-id and obviously cannot be omitted;
--** if the referenced artefact is a Dimension, TimeDimension, Measure, DataAttribute, which are not maintainable and belong to the DataStructure maintainable class, the maintainedobject-id is the dataStructure-id and can be omitted, given that these components are always invoked within the invocation of a Dataflow, whose dataStructure-id can be deduced from the SDMX structural definitions;
--** if the referenced artefact is a Concept, which is not maintainable and belong to the ConceptScheme maintainable class, the maintained object is the conceptScheme-id and cannot be omitted;
--** if the referenced artefact is a Codelist, which is a maintainable class, the maintainedobject-id is the codelist-id and obviously cannot be omitted.
--* When the maintainedobject-id is omitted, the maintainedobject-version is omitted too. When the maintainedobject-id is not omitted and the maintainedobject-version is omitted, the version 1.0 is assumed by default.
--* As said, the container-object-id does not apply to the classes that can be referenced in VTL Transformations, therefore is not present in their URN
--* The object-id does not exist for the artefacts belonging to the Dataflow, and Codelist classes, while it exists and cannot be omitted for the artefacts belonging to the classes Dimension, TimeDimension, Measure, DataAttribute and Concept, as for them the object-id is the main identifier of the artefact
++** if the referenced [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], which is a maintainable class, the maintainedobject-id is the [[dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]]-id and obviously cannot be omitted;
++** if the referenced [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], TimeDimension, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]], DataAttribute, which are not maintainable and belong to the DataStructure maintainable class, the maintainedobject-id is the dataStructure-id and can be omitted, given that these [[components>>doc:sdmx:Glossary.Component.WebHome]] are always invoked within the invocation of a [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], whose dataStructure-id can be deduced from the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] structural definitions;
++** if the referenced [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a (% style="color:#e74c3c" %)Concept(%%), which is not maintainable and belong to the ConceptScheme maintainable class, the maintained object is the conceptScheme-id and cannot be omitted;
++** if the referenced [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a Codelist, which is a maintainable class, the maintainedobject-id is the codelist-id and obviously cannot be omitted.
++* When the maintainedobject-id is omitted, the maintainedobject-(% style="color:#e74c3c" %)version(%%) is omitted too. When the maintainedobject-id is not omitted and the maintainedobject-(% style="color:#e74c3c" %)version(%%) is omitted, the (% style="color:#e74c3c" %)version(%%) 1.0 is assumed by default.
++* As said, the container-object-id does not apply to the classes that can be referenced in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations, therefore is not present in their URN
++* The object-id does not exist for the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] belonging to the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], and Codelist classes, while it exists and cannot be omitted for the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] belonging to the classes [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], TimeDimension, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]], DataAttribute and (% style="color:#e74c3c" %)Concept(%%), as for them the object-id is the main identifier of the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]]
  The simplified object identifier is obtained by omitting all the first part of the URN, including the special characters, till the first part not omitted.
@@ -116,7 +116,7 @@
  by omitting all the non-essential parts would become simply:
--> DFR   : =  DF1 + DF2
++> DFR : = DF1 + DF2
  The references to the Codelists can be simplified similarly. For example, given the non-abbreviated reference to the Codelist AG:CL_FREQ(1.0.0), which is{{footnote}}Single quotes are needed because this reference is not a VTL regular name. 19 Single quotes are not needed in this case because CL_FREQ is a VTL regular name.{{/footnote}}:
@@ -126,7 +126,7 @@
  > CL_FREQ
--As for the references to the components, it can be enough to specify the componentId, given that the dataStructure-Id can be omitted. An example of non-abbreviated reference, if the data structure is DST1 and the component is SECTOR, is the following:
++As for the references to the [[components>>doc:sdmx:Glossary.Component.WebHome]], it can be enough to specify the componentId, given that the dataStructure-Id can be omitted. An example of non-abbreviated reference, if the data structure is DST1 and the [[component>>doc:sdmx:Glossary.Component.WebHome]] is SECTOR, is the following:
  > 'urn:sdmx:org.sdmx.infomodel.datastructure.DataStructure=AG:DST1(1.0.0).S ECTOR'
@@ -134,13 +134,13 @@
  > SECTOR
--For example, the Transformation for renaming the component SECTOR of the Dataflow DF1 into SEC can be written as{{footnote}}The result DFR(1.0.0) is be equal to DF1(1.0.0) save that the component SECTOR is called SEC{{/footnote}}:
++For example, the Transformation for renaming the [[component>>doc:sdmx:Glossary.Component.WebHome]] SECTOR of the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF1 into SEC can be written as{{footnote}}The result DFR(1.0.0) is be equal to DF1(1.0.0) save that the component SECTOR is called SEC{{/footnote}}:
  > 'DFR(1.0.0)' := 'DF1(1.0.0)' [rename SECTOR to SEC]
--In the references to the Concepts, which can exist for example in the definition of the VTL Rulesets, at least the conceptScheme-id and the concept-id must be specified.
++In the references to the (% style="color:#e74c3c" %)Concepts(%%), which can exist for example in the definition of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Rulesets, at least the conceptScheme-id and the (% style="color:#e74c3c" %)concept(%%)-id must be specified.
--An example of non-abbreviated reference, if the conceptScheme-id is CS1 and the concept-id is SECTOR, is the following:
++An example of non-abbreviated reference, if the conceptScheme-id is CS1 and the (% style="color:#e74c3c" %)concept(%%)-id is SECTOR, is the following:
  > 'urn:sdmx:org.sdmx.infomodel.conceptscheme.Concept=AG:CS1(1.0.0).SECTOR'
@@ -148,53 +148,53 @@
  > CS1(1.0.0).SECTOR
--The Codes and in general all the Values can be written without any other specification, for example, the transformation to check if the values of the measures of the Dataflow DF1 are between 0 and 25000 can be written like follows:
++The [[Codes>>doc:sdmx:Glossary.Code.WebHome]] and in general all the Values can be written without any other specification, for example, the transformation to check if the values of the [[measures>>doc:sdmx:Glossary.Measure.WebHome]] of the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF1 are between 0 and 25000 can be written like follows:
  > 'DFR(1.0.0)' := between ( 'DF1(1.0.0)', 0, 25000 )
--The artefact (Component, Concept, Codelist …) which the Values are referred to can be deduced from the context in which the reference is made, taking also into account the VTL syntax. In the Transformation above, for example, the values 0 and 2500 are compared to the values of the measures of DF1(1.0.0).
++The [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] ([[Component>>doc:sdmx:Glossary.Component.WebHome]], (% style="color:#e74c3c" %)Concept(%%), Codelist …) which the Values are referred to can be deduced from the context in which the reference is made, taking also into account the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] syntax. In the Transformation above, for example, the values 0 and 2500 are compared to the values of the [[measures>>doc:sdmx:Glossary.Measure.WebHome]] of DF1(1.0.0).
  === 12.2.4 User-defined alias ===
--The third possibility for referencing SDMX artefacts from VTL statements is to use user-defined aliases not related to the SDMX URN of the artefact.
++The third possibility for referencing [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] statements is to use user-defined aliases not related to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] URN of the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]].
--This approach gives preference to the use of symbolic names for the SDMX artefacts. As a consequence, in the VTL code the referenced artefacts may become not directly intelligible by a human reader. In any case, the VTL aliases are associated to the SDMX URN through the VtlMappingScheme and VtlMapping classes. These classes provide for structured references to SDMX artefacts whatever kind of reference is used in VTL statements (URN, abbreviated URN or user-defined aliases).
++This approach gives preference to the use of symbolic names for the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]]. As a consequence, in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[code>>doc:sdmx:Glossary.Code.WebHome]] the referenced [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] may become not directly intelligible by a human reader. In any case, the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] aliases are associated to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] URN through the VtlMappingScheme and VtlMapping classes. These classes provide for structured references to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] whatever kind of reference is used in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] statements (URN, abbreviated URN or user-defined aliases).
  === 12.2.5 References to SDMX artefacts from VTL Rulesets ===
--The VTL Rulesets allow defining sets of reusable Rules that can be applied by some VTL operators, like the ones for validation and hierarchical roll-up. A "Rule" consists in a relationship between Values belonging to some Value Domains or taken by some Variables, for example: (i) when the Country is USA then the Currency is USD; (ii) the Benelux is composed by Belgium, Luxembourg, Netherlands.
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Rulesets allow defining sets of reusable Rules that can be applied by some [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operators, like the ones for validation and hierarchical roll-up. A "Rule" consists in a relationship between Values belonging to some Value Domains or taken by some Variables, for example: when the Country is USA then the [[Currency>>doc:sdmx:Glossary.Currency.WebHome]] is USD; (ii) the Benelux is composed by Belgium, Luxembourg, Netherlands.
--The VTL Rulesets have a signature, in which the Value Domains or the Variables on which the Ruleset is defined are declared, and a body, which contains the Rules.
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Rulesets have a signature, in which the Value Domains or the Variables on which the Ruleset is defined are declared, and a body, which contains the Rules.
--In the signature, given the mapping between VTL and SDMX better described in the following paragraphs, a reference to a VTL Value Domain becomes a reference to a SDMX Codelist, while a reference to a VTL Represented Variable becomes a reference to a SDMX Concept, assuming for it a definite representation{{footnote}}Rulesets of this kind cannot be reused when the referenced Concept has a different representation.{{/footnote}}.
++In the signature, given the mapping between [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] better described in the following paragraphs, a reference to a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Value Domain becomes a reference to a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Codelist, while a reference to a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Represented Variable becomes a reference to a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (% style="color:#e74c3c" %)Concept(%%), assuming for it a definite [[representation>>doc:sdmx:Glossary.Representation.WebHome]]{{footnote}}Rulesets of this kind cannot be reused when the referenced Concept has a different representation.{{/footnote}}.
--In general, for referencing SDMX Codelists and Concepts, the conventions described in the previous paragraphs apply. In the Ruleset syntax, the elements that reference SDMX artefacts are called "valueDomain" and "variable" for the Datapoint Rulesets and "ruleValueDomain", "ruleVariable", "condValueDomain" "condVariable" for the Hierarchical Rulesets). The syntax of the Ruleset signature allows also to define aliases of the elements above, these aliases are valid only within the specific Ruleset definition statement and cannot be mapped to SDMX.{{footnote}}See also the section "VTL-DL Rulesets" in the VTL Reference Manual.{{/footnote}}
++In general, for referencing [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Codelists and (% style="color:#e74c3c" %)Concepts(%%), the conventions described in the previous paragraphs apply. In the Ruleset syntax, the elements that reference [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] are called "valueDomain" and "variable" for the Datapoint Rulesets and "ruleValueDomain", "ruleVariable", "condValueDomain" "condVariable" for the Hierarchical Rulesets). The syntax of the Ruleset signature allows also to define aliases of the elements above, these aliases are valid only within the specific Ruleset definition statement and cannot be (% style="color:#e74c3c" %)mapped(%%) to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]].{{footnote}}See also the section "VTL-DL Rulesets" in the VTL Reference Manual.{{/footnote}}
--In the body of the Rulesets, the Codes and in general all the Values can be written without any other specification, because the artefact, which the Values are referred (Codelist, Concept) to can be deduced from the Ruleset signature.
++In the body of the Rulesets, the [[Codes>>doc:sdmx:Glossary.Code.WebHome]] and in general all the Values can be written without any other specification, because the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]], which the Values are referred (Codelist, (% style="color:#e74c3c" %)Concept(%%)) to can be deduced from the Ruleset signature.
  == 12.3 Mapping between SDMX and VTL artefacts ==
  === 12.3.1. When the mapping occurs ===
--The mapping methods between the VTL and SDMX object classes allow transforming a SDMX definition in a VTL one and vice-versa for the artefacts to be manipulated. It should be remembered that VTL programs (i.e. Transformation Schemes) are represented in SDMX through the TransformationScheme maintainable class which is composed of Transformations (nameable artefacts). Each Transformation assigns the outcome of the evaluation of a VTL expression to a result: the input operands of the expression and the result can be SDMX artefacts. Every time a SDMX object is referenced in a VTL Transformation as an input operand, there is the need to generate a VTL definition of the object, so that the VTL operations can take place. This can be made starting from the SDMX definition and applying a SDMX-VTL mapping method in the direction from SDMX to VTL. The possible mapping methods from SDMX to VTL are described in the following paragraphs and are conceived to allow the automatic deduction of the VTL definition of the object from the knowledge of the SDMX definition.
++The mapping methods between the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] object classes allow transforming a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definition in a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] one and vice-versa for the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] to be manipulated. It should be remembered that [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] programs (i.e. Transformation Schemes) are represented in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] through the TransformationScheme maintainable class which is composed of Transformations ([[nameable artefacts>>doc:sdmx:Glossary.Nameable artefact.WebHome]]). Each Transformation assigns the outcome of the evaluation of a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] expression to a result: the input operands of the expression and the result can be [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]]. Every time a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] object is referenced in a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformation as an input operand, there is the need to generate a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] definition of the object, so that the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operations can take place. This can be made starting from the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definition and applying a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]-[[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] mapping method in the direction from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]. The possible mapping methods from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] are described in the following paragraphs and are conceived to allow the automatic deduction of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] definition of the object from the knowledge of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definition.
--In the opposite direction, every time an object calculated by means of VTL must be treated as a SDMX object (for example for exchanging it through SDMX), there is the need of a SDMX definition of the object, so that the SDMX operations can take place. The SDMX definition is needed for the VTL objects for which a SDMX use is envisaged{{footnote}}If a calculated artefact is persistent, it needs a persistent definition, i.e. a SDMX definition in a SDMX environment. In addition, possible calculated artefact that are not persistent may require a SDMX definition, for example when the result of a nonpersistent calculation is disseminated through SDMX tools (like an inquiry tool).{{/footnote}}.
++In the opposite direction, every time an object calculated by means of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] must be treated as a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] object (for example for exchanging it through [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]), there is the need of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definition of the object, so that the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] operations can take place. The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definition is needed for the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] objects for which a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] use is envisaged{{footnote}}If a calculated artefact is persistent, it needs a persistent definition, i.e. a SDMX definition in a SDMX environment. In addition, possible calculated artefact that are not persistent may require a SDMX definition, for example when the result of a nonpersistent calculation is disseminated through SDMX tools (like an inquiry tool).{{/footnote}}.
--The mapping methods from VTL to SDMX are described in the following paragraphs as well, however they do not allow the complete SDMX definition to be automatically deduced from the VTL definition, more than all because the former typically contains additional information in respect to the latter. For example, the definition of a SDMX DSD includes also some mandatory information not available in VTL (like the concept scheme to which the SDMX components refer, the ‘usage’ and ‘attributeRelationship’ for the DataAttributes and so on). Therefore the mapping methods from VTL to SDMX provide only a general guidance for generating SDMX definitions properly starting from the information available in VTL, independently of how the SDMX definition it is actually generated (manually, automatically or part and part).
++The mapping methods from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] are described in the following paragraphs as well, however they do not allow the complete [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definition to be automatically deduced from the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] definition, more than all because the former typically contains additional information in respect to the latter. For example, the definition of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[DSD>>doc:sdmx:Glossary.Data structure definition.WebHome]] includes also some mandatory information not available in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (like the [[concept scheme>>doc:sdmx:Glossary.Concept scheme.WebHome]] to which the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[components>>doc:sdmx:Glossary.Component.WebHome]] refer, the ‘usage’ and ‘attributeRelationship’ for the DataAttributes and so on). Therefore the mapping methods from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] provide only a general guidance for generating [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definitions properly starting from the information available in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], independently of how the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definition it is actually generated (manually, automatically or part and part).
  === 12.3.2 General mapping of VTL and SDMX data structures ===
--This section makes reference to the VTL "Model for data and their structure"{{footnote}}See the VTL 2.0 User Manual{{/footnote}} and the correspondent SDMX "Data Structure Definition"{{footnote}}See the SDMX Standards Section 2 – Information Model{{/footnote}}.
++This section makes reference to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] "Model for data and their structure"{{footnote}}See the VTL 2.0 User Manual{{/footnote}} and the correspondent [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] "Data Structure Definition"{{footnote}}See the SDMX Standards Section 2 – Information Model{{/footnote}}.
--The main type of artefact that the VTL can manipulate is the VTL Data Set, which in general is mapped to the SDMX Dataflow. This means that a VTL Transformation, in the SDMX context, expresses the algorithm for calculating a derived Dataflow starting from some already existing Dataflows (either collected or derived).{{footnote}}Besides the mapping between one SDMX Dataflow and one VTL Data Set, it is also possible to map distinct parts of a SDMX Dataflow to different VTL Data Set, as explained in a following paragraph.{{/footnote}}
++The main type of [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] that the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] can manipulate is the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]], which in general is (% style="color:#e74c3c" %)mapped(%%) to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]]. This means that a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformation, in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] context, expresses the algorithm for calculating a derived [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] starting from some already existing [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]] (either collected or derived).{{footnote}}Besides the mapping between one SDMX Dataflow and one VTL Data Set, it is also possible to map distinct parts of a SDMX Dataflow to different VTL Data Set, as explained in a following paragraph.{{/footnote}}
--While the VTL Transformations are defined in term of Dataflow definitions, they are assumed to be executed on instances of such Dataflows, provided at runtime to the VTL engine (the mechanism for identifying the instances to be processed are not part of the VTL specifications and depend on the implementation of the VTL-based systems). As already said, the SDMX Datasets are instances of SDMX Dataflows, therefore a VTL Transformation defined on some SDMX Dataflows can be applied on some corresponding SDMX Datasets.
++While the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations are defined in term of [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] definitions, they are assumed to be executed on instances of such [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]], provided at runtime to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] engine (the mechanism for identifying the instances to be processed are not part of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] specifications and depend on the implementation of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]-based systems). As already said, the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Datasets>>doc:sdmx:Glossary.Data set.WebHome]] are instances of [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]], therefore a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformation defined on some [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]] can be applied on some corresponding [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Datasets>>doc:sdmx:Glossary.Data set.WebHome]].
--A VTL Data Set is structured by one and just one Data Structure and a VTL Data Structure can structure any number of Data Sets. Correspondingly, in the SDMX context a SDMX Dataflow is structured by one and just one DataStructureDefinition and one DataStructureDefinition can structure any number of Dataflows.
++A [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] is structured by one and just one Data Structure and a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Data Structure can structure any number of [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]]. Correspondingly, in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] context a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] is structured by one and just one DataStructureDefinition and one DataStructureDefinition can structure any number of [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]].
--A VTL Data Set has a Data Structure made of Components, which in turn can be Identifiers, Measures and Attributes. Similarly, a SDMX DataflowDefinition has a DataStructureDefinition made of components that can be DimensionComponents, Measure and DataAttributes. In turn, a SDMX DimensionComponent can be a Dimension or a TimeDimension.
++A [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] has a Data Structure made of [[Components>>doc:sdmx:Glossary.Component.WebHome]], which in turn can be Identifiers, [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] and [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]]. Similarly, a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataflowDefinition has a DataStructureDefinition made of [[components>>doc:sdmx:Glossary.Component.WebHome]] that can be DimensionComponents, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] and DataAttributes. In turn, a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponent can be a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] or a TimeDimension.
--Correspondingly, in the SDMX implementation of the VTL, the VTL Identifiers can be (optionally) distinguished in similar sub-classes (Simple Identifier, Time Identifier) even if such a distinction is not evidenced in the VTL IM.
++Correspondingly, in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] implementation of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Identifiers can be (optionally) distinguished in similar sub-classes (Simple Identifier, Time Identifier) even if such a distinction is not evidenced in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] IM.
  The possible mapping options are described in more detail in the following sections.
@@ -202,634 +202,627 @@
  ==== 12.3.3.1 Basic Mapping ====
--The main mapping method from SDMX to VTL is called **Basic **mapping. This is considered as the default mapping method and is applied unless a different method is specified through the VtlMappingScheme and VtlDataflowMapping classes.
++The main mapping method from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] is called **Basic **mapping. This is considered as the default mapping method and is applied unless a different method is specified through the VtlMappingScheme and VtlDataflowMapping classes.
--When transforming **from SDMX to VTL**, this method consists in leaving the components unchanged and maintaining their names and roles, according to the following table:
++When transforming **from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]**, this method consists in leaving the [[components>>doc:sdmx:Glossary.Component.WebHome]] unchanged and maintaining their names and roles, according to the following table:
  (% style="width:468.294px" %)
--|(% style="width:196px" %)**SDMX**|(% style="width:269px" %)**VTL**
--|(% style="width:196px" %)Dimension|(% style="width:269px" %)(Simple) Identifier
++|(% style="width:196px" %)**[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]**|(% style="width:269px" %)**[[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]**
++|(% style="width:196px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]|(% style="width:269px" %)(Simple) Identifier
  |(% style="width:196px" %)TimeDimension|(% style="width:269px" %)(Time) Identifier
--|(% style="width:196px" %)Measure|(% style="width:269px" %)Measure
--|(% style="width:196px" %)DataAttribute|(% style="width:269px" %)Attribute
++|(% style="width:196px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:269px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]
++|(% style="width:196px" %)DataAttribute|(% style="width:269px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]
--The SDMX DataAttributes, in VTL they are all considered "at data point / observation level" (i.e. dependent on all the VTL Identifiers), because VTL does not have the SDMX AttributeRelationships, which defines the construct to which the DataAttribute is related (e.g. observation, dimension or set or group of dimensions, whole data set).
++The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes, in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] they are all considered "at data point / observation (% style="color:#e74c3c" %)level(%%)" (i.e. dependent on all the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Identifiers), because [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] does not have the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] AttributeRelationships, which defines the construct to which the DataAttribute is related (e.g. observation, [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] or set or group of [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]], whole [[data set>>doc:sdmx:Glossary.Data set.WebHome]]).
--With the Basic mapping, one SDMX observation^^27^^ generates one VTL data point.
++With the Basic mapping, one [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] observation^^27^^ generates one [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data point.
  ==== 12.3.3.2 Pivot Mapping ====
--An alternative mapping method from SDMX to VTL is the **Pivot **mapping, which makes sense and is different from the Basic method only for the SDMX data structures that contain a Dimension that plays the role of measure dimension (like in SDMX 2.1) and just one Measure. Through this method, these structures can be mapped to multimeasure VTL data structures. Besides that, a user may choose to use any Dimension acting as a list of Measures (e.g., a Dimension with indicators), either by considering the “Measure” role of a Dimension, or at will using any coded Dimension. Of course, in SDMX 3.0, this can only work when only one Measure is defined in the DSD.
++An alternative mapping method from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] is the **Pivot **mapping, which makes sense and is different from the Basic method only for the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data structures that contain a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] that plays the role of [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] (like in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1) and just one [[Measure>>doc:sdmx:Glossary.Measure.WebHome]]. Through this method, these structures can be (% style="color:#e74c3c" %)mapped(%%) to multimeasure [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data structures. Besides that, a user may choose to use any [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] acting as a list of [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] (e.g., a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] with indicators), either by considering the “[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]” role of a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], or at will using any coded [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]. Of course, in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 3.0, this can only work when only one [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] is defined in the [[DSD>>doc:sdmx:Glossary.Data structure definition.WebHome]].
--In SDMX 2.1 the MeasureDimension was a subclass of DimensionComponent like Dimension and TimeDimension. In the current SDMX version, this subclass does not exist anymore, however a Dimension can have the role of measure dimension (i.e. a Dimension that contributes to the identification of the measures). In SDMX 2.1 a DataStructure could have zero or one MeasureDimensions, in the current version of the standard, from zero to many Dimension may have the role of measure dimension. Hereinafter a Dimension that plays the role of measure dimension is referenced for simplicity as “MeasureDimension“, i.e. maintaining the capital letters and the courier font even if the MeasureDimension is not anymore a class in the SDMX Information Model of the current SDMX version. For the sake of simplicity, the description below considers just one Dimension having the role of MeasureDimension (i.e., the more simple and common case). Nevertheless, it maintains its validity also if in the DataStructure there are more dimension with the role of MeasureDimensions: in this case what is said about the MeasureDimension must be applied to the combination of all the MeasureDimensions considered as a joint variable{{footnote}}E.g., if in the data structure there exist 3 Dimensions C,D,E having the role of MeasureDimension, they should be considered as a joint MeasureDimension Z=(C,D,E); therefore when the description says “each possible value Cj of the MeasureDimension …” it means “each possible combination of values (Cj, Dk, Ew) of the joint MeasureDimension Z=(C,D,E)”.{{/footnote}}.
++In [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 the MeasureDimension was a subclass of DimensionComponent like [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] and TimeDimension. In the current [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (% style="color:#e74c3c" %)version(%%), this subclass does not exist anymore, however a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] can have the role of [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] (i.e. a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] that contributes to the identification of the [[measures>>doc:sdmx:Glossary.Measure.WebHome]]). In [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 a DataStructure could have zero or one MeasureDimensions, in the current (% style="color:#e74c3c" %)version(%%) of the standard, from zero to many [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] may have the role of [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]]. Hereinafter a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] that plays the role of [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] is referenced for simplicity as “MeasureDimension“, i.e. maintaining the capital letters and the courier font even if the MeasureDimension is not anymore a class in the [[SDMX Information Model>>doc:sdmx:Glossary.SDMX Information Model.WebHome]] of the current [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (% style="color:#e74c3c" %)version(%%). For the sake of simplicity, the description below considers just one [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] having the role of MeasureDimension (i.e., the more simple and common case). Nevertheless, it maintains its validity also if in the DataStructure there are more [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] with the role of MeasureDimensions: in this case what is said about the MeasureDimension must be applied to the combination of all the MeasureDimensions considered as a joint variable{{footnote}}E.g., if in the data structure there exist 3 Dimensions C,D,E having the role of MeasureDimension, they should be considered as a joint MeasureDimension Z=(C,D,E); therefore when the description says “each possible value Cj of the MeasureDimension …” it means “each possible combination of values (Cj, Dk, Ew) of the joint MeasureDimension Z=(C,D,E)”.{{/footnote}}.
--Among other things, the Pivot method provides also backward compatibility with the SDMX 2.1 data structures that contained a MeasureDimension.
++Among other things, the Pivot method provides also backward compatibility with the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 data structures that contained a MeasureDimension.
--If applied to SDMX structures that do not contain any MeasureDimension, this method behaves like the Basic mapping (see the previous paragraph).
++If applied to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] structures that do not contain any MeasureDimension, this method behaves like the Basic mapping (see the previous paragraph).
--The SDMX structures that contain a MeasureDimension are mapped as described below (this mapping is equivalent to a pivoting operation):
++The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] structures that contain a MeasureDimension are (% style="color:#e74c3c" %)mapped(%%) as described below (this mapping is equivalent to a pivoting operation):
--* A SDMX simple dimension becomes a VTL (simple) identifier and a SDMX TimeDimension becomes a VTL (time) identifier;
--* Each possible Code Cj of the SDMX MeasureDimension is mapped to a VTL Measure, having the same name as the SDMX Code (i.e. Cj); the VTL Measure Cj is a new VTL component even if the SDMX data structure has not such a Component;
--* The SDMX MeasureDimension is not mapped to VTL (it disappears in the VTL Data Structure);
--* The SDMX Measure is not mapped to VTL as well (it disappears in the VTL Data Structure);
--* An SDMX DataAttribute is mapped in different ways according to its AttributeRelationship:
--** If, according to the SDMX AttributeRelationship, the values of the DataAttribute do not depend on the values of the MeasureDimension, the SDMX DataAttribute becomes a VTL Attribute having the same name. This happens if the AttributeRelationship is not specified (i.e. the DataAttribute does not depend on any DimensionComponent and therefore is at data set level), or if it refers to a set (or a group) of dimensions which does not include the MeasureDimension;
--** Otherwise, if, according to the SDMX AttributeRelationship, the values of the DataAttribute depend on the MeasureDimension, the SDMX DataAttribute is mapped to one VTL Attribute for each possible Code of the SDMX MeasureDimension. By default, the names of the VTL Attributes are obtained by concatenating the name of the SDMX DataAttribute and the names of the correspondent Code of the MeasureDimension separated by underscore. For example, if the SDMX DataAttribute is named DA and the possible Codes of the SDMX MeasureDimension are named C1, C2, …, Cn, then the corresponding VTL Attributes will be named DA_C1, DA_C2, …, DA_Cn (if different names are desired, they can be achieved afterwards by renaming the Attributes through VTL operators).
--** Like in the Basic mapping, the resulting VTL Attributes are considered as dependent on all the VTL identifiers (i.e. "at data point / observation level"), because VTL does not have the SDMX notion of Attribute Relationship.
++* A [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] simple [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] becomes a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (simple) identifier and a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] TimeDimension becomes a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (time) identifier;
++* Each possible [[Code>>doc:sdmx:Glossary.Code.WebHome]] Cj of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension is (% style="color:#e74c3c" %)mapped(%%) to a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]], having the same name as the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Code>>doc:sdmx:Glossary.Code.WebHome]] (i.e. Cj); the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] Cj is a new [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]] even if the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data structure has not such a [[Component>>doc:sdmx:Glossary.Component.WebHome]];
++* The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension is not (% style="color:#e74c3c" %)mapped(%%) to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (it disappears in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Data Structure);
++* The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] is not (% style="color:#e74c3c" %)mapped(%%) to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] as well (it disappears in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Data Structure);
++* An [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute is (% style="color:#e74c3c" %)mapped(%%) in different ways according to its AttributeRelationship:
++** If, according to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] AttributeRelationship, the values of the DataAttribute do not depend on the values of the MeasureDimension, the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute becomes a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] having the same name. This happens if the AttributeRelationship is not specified (i.e. the DataAttribute does not depend on any DimensionComponent and therefore is at [[data set>>doc:sdmx:Glossary.Data set.WebHome]] (% style="color:#e74c3c" %)level(%%)), or if it refers to a set (or a group) of [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] which does not include the MeasureDimension;
++** Otherwise, if, according to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] AttributeRelationship, the values of the DataAttribute depend on the MeasureDimension, the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute is (% style="color:#e74c3c" %)mapped(%%) to one [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] for each possible [[Code>>doc:sdmx:Glossary.Code.WebHome]] of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension. By default, the names of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]] are obtained by concatenating the name of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute and the names of the correspondent [[Code>>doc:sdmx:Glossary.Code.WebHome]] of the MeasureDimension separated by underscore. For example, if the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute is named DA and the possible [[Codes>>doc:sdmx:Glossary.Code.WebHome]] of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension are named C1, C2, …, Cn, then the corresponding [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]] will be named DA_C1, DA_C2, …, DA_Cn (if different names are desired, they can be achieved afterwards by renaming the [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]] through [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operators).
++** Like in the Basic mapping, the resulting [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]] are considered as dependent on all the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] identifiers (i.e. "at data point / observation (% style="color:#e74c3c" %)level(%%)"), because [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] does not have the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] notion of [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] Relationship.
--The summary mapping table of the "pivot" mapping from SDMX to VTL for the SDMX data structures that contain a MeasureDimension is the following:
++The summary mapping table of the "pivot" mapping from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] for the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data structures that contain a MeasureDimension is the following:
  (% style="width:739.294px" %)
--|(% style="width:335px" %)**SDMX**|(% style="width:400px" %)**VTL**
--|(% style="width:335px" %)Dimension|(% style="width:400px" %)(Simple) Identifier
++|(% style="width:335px" %)**[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]**|(% style="width:400px" %)**[[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]**
++|(% style="width:335px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]|(% style="width:400px" %)(Simple) Identifier
  |(% style="width:335px" %)TimeDimension|(% style="width:400px" %)(Time) Identifier
--|(% style="width:335px" %)MeasureDimension & one Measure|(% style="width:400px" %)One Measure for each Code of the SDMX MeasureDimension
--|(% style="width:335px" %)DataAttribute not depending on the MeasureDimension|(% style="width:400px" %)Attribute
++|(% style="width:335px" %)MeasureDimension & one [[Measure>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:400px" %)One [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] for each [[Code>>doc:sdmx:Glossary.Code.WebHome]] of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension
++|(% style="width:335px" %)DataAttribute not depending on the MeasureDimension|(% style="width:400px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]
  |(% style="width:335px" %)DataAttribute depending on the MeasureDimension|(% style="width:400px" %)(((
--One Attribute for each Code of the
--SDMX MeasureDimension
++One [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] for each [[Code>>doc:sdmx:Glossary.Code.WebHome]] of the
++[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension
  )))
--Using this mapping method, the components of the data structure can change in the conversion from SDMX to VTL and it must be taken into account that the VTL statements can reference only the components of the resulting VTL data structure.
++Using this mapping method, the [[components>>doc:sdmx:Glossary.Component.WebHome]] of the data structure can change in the conversion from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and it must be taken into account that the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] statements can reference only the [[components>>doc:sdmx:Glossary.Component.WebHome]] of the resulting [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data structure.
--At observation / data point level, calling Cj (j=1, … n) the j^^th^^ Code of the MeasureDimension:
++At observation / data point (% style="color:#e74c3c" %)level(%%), calling Cj (j=1, … n) the j^^th^^ [[Code>>doc:sdmx:Glossary.Code.WebHome]] of the MeasureDimension:
--* The set of SDMX observations having the same values for all the Dimensions except than the MeasureDimension become one multi-measure VTL Data Point, having one Measure for each Code Cj of the SDMX MeasureDimension;
--* The values of the SDMX simple Dimensions, TimeDimension and DataAttributes not depending on the MeasureDimension (these components by definition have always the same values for all the observations of the set above) become the values of the corresponding VTL (simple) Identifiers, (time) Identifier and Attributes.
--* The value of the Measure of the SDMX observation belonging to the set above and having MeasureDimension=Cj becomes the value of the VTL Measure Cj
--* For the SDMX DataAttributes depending on the MeasureDimension, the value of the DataAttribute DA of the SDMX observation belonging to the set above and having MeasureDimension=Cj becomes the value of the VTL Attribute DA_Cj
++* The set of [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] observations having the same values for all the [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] except than the MeasureDimension become one multi-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Data Point, having one [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] for each [[Code>>doc:sdmx:Glossary.Code.WebHome]] Cj of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension;
++* The values of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] simple [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]], TimeDimension and DataAttributes not depending on the MeasureDimension (these [[components>>doc:sdmx:Glossary.Component.WebHome]] by definition have always the same values for all the observations of the set above) become the values of the corresponding [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (simple) Identifiers, (time) Identifier and [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]].
++* The value of the [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] observation belonging to the set above and having MeasureDimension=Cj becomes the value of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] Cj
++* For the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes depending on the MeasureDimension, the value of the DataAttribute DA of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] observation belonging to the set above and having MeasureDimension=Cj becomes the value of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] DA_Cj
  ==== 12.3.3.3 From SDMX DataAttributes to VTL Measures ====
--* In some cases, it may happen that the DataAttributes of the SDMX DataStructure need to be managed as Measures in VTL. Therefore, a variant of both the methods above consists in transforming all the SDMX DataAttributes in VTL Measures. When DataAttributes are converted to Measures, the two methods above are called Basic_A2M and Pivot_A2M (the suffix "A2M" stands for Attributes to Measures). Obviously, the resulting VTL data structure is, in general, multi-measure and does not contain Attributes.
++* In some cases, it may happen that the DataAttributes of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure need to be managed as [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]. Therefore, a variant of both the methods above consists in transforming all the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:sdmx:Glossary.Measure.WebHome]]. When DataAttributes are converted to [[Measures>>doc:sdmx:Glossary.Measure.WebHome]], the two methods above are called Basic_A2M and Pivot_A2M (the suffix "A2M" stands for [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]] to [[Measures>>doc:sdmx:Glossary.Measure.WebHome]]). Obviously, the resulting [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data structure is, in general, multi-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] and does not contain [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]].
--The Basic_A2M and Pivot_A2M behaves respectively like the Basic and Pivot methods, except that the final VTL components, which according to the Basic and Pivot methods would have had the role of Attribute, assume instead the role of Measure.
++The Basic_A2M and Pivot_A2M behaves respectively like the Basic and Pivot methods, except that the final [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[components>>doc:sdmx:Glossary.Component.WebHome]], which according to the Basic and Pivot methods would have had the role of [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]], assume instead the role of [[Measure>>doc:sdmx:Glossary.Measure.WebHome]].
--Proper VTL features allow changing the role of specific attributes even after the SDMX to VTL mapping: they can be useful when only some of the DataAttributes need to be managed as VTL Measures.
++Proper [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] features allow changing the role of specific [[attributes>>doc:sdmx:Glossary.Attribute.WebHome]] even after the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] mapping: they can be useful when only some of the DataAttributes need to be managed as [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:sdmx:Glossary.Measure.WebHome]].
  === 12.3.4 Mapping from VTL to SDMX data structures ===
  ==== 12.3.4.1 Basic Mapping ====
--The main mapping method **from VTL to SDMX** is called **Basic **mapping as well.
++The main mapping method **from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]** is called **Basic **mapping as well.
  This is considered as the default mapping method and is applied unless a different method is specified through the VtlMappingScheme and VtlDataflowMapping classes.
--The method consists in leaving the components unchanged and maintaining their names and roles in SDMX, according to the following mapping table, which is the same as the basic mapping from SDMX to VTL, only seen in the opposite direction.
++The method consists in leaving the [[components>>doc:sdmx:Glossary.Component.WebHome]] unchanged and maintaining their names and roles in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], according to the following mapping table, which is the same as the basic mapping from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], only seen in the opposite direction.
  Mapping table:
  (% style="width:470.294px" %)
--|(% style="width:262px" %)**VTL**|(% style="width:205px" %)**SDMX**
--|(% style="width:262px" %)(Simple) Identifier|(% style="width:205px" %)Dimension
++|(% style="width:262px" %)**[[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]**|(% style="width:205px" %)**[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]**
++|(% style="width:262px" %)(Simple) Identifier|(% style="width:205px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]
  |(% style="width:262px" %)(Time) Identifier|(% style="width:205px" %)TimeDimension
--|(% style="width:262px" %)Measure|(% style="width:205px" %)Measure
--|(% style="width:262px" %)Attribute|(% style="width:205px" %)DataAttribute
++|(% style="width:262px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:205px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]
++|(% style="width:262px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]|(% style="width:205px" %)DataAttribute
--If the distinction between simple identifier and time identifier is not maintained in the VTL environment, the classification between Dimension and TimeDimension exists only in SDMX, as declared in the relevant DataStructureDefinition.
++If the distinction between simple identifier and time identifier is not maintained in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] environment, the classification between [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] and TimeDimension exists only in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], as declared in the relevant DataStructureDefinition.
--Regarding the Attributes, because VTL considers all of them "at observation level", the corresponding SDMX DataAttributes should be put "at observation level" as well, unless some different information about their AttributeRelationship is otherwise available.
++Regarding the [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]], because [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] considers all of them "at observation (% style="color:#e74c3c" %)level(%%)", the corresponding [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes should be put "at observation (% style="color:#e74c3c" %)level(%%)" as well, unless some different information about their AttributeRelationship is otherwise available.
--Note that the basic mappings in the two directions (from SDMX to VTL and vice-versa) are (almost completely) reversible. In fact, if a SDMX structure is mapped to a VTL structure and then the latter is mapped back to SDMX, the resulting data structure is like the original one (apart for the AttributeRelationship, that can be different if the original SDMX structure contains DataAttributes that are not at observation level). In reverse order, if a VTL structure is mapped to SDMX and then the latter is mapped back to VTL, the original data structure is obtained.
++Note that the basic mappings in the two directions (from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and vice-versa) are (almost completely) reversible. In fact, if a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] structure is (% style="color:#e74c3c" %)mapped(%%) to a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structure and then the latter is (% style="color:#e74c3c" %)mapped(%%) back to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], the resulting data structure is like the original one (apart for the AttributeRelationship, that can be different if the original [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] structure contains DataAttributes that are not at observation (% style="color:#e74c3c" %)level(%%)). In reverse order, if a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structure is (% style="color:#e74c3c" %)mapped(%%) to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] and then the latter is (% style="color:#e74c3c" %)mapped(%%) back to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], the original data structure is obtained.
--As said, the resulting SDMX definitions must be compliant with the SDMX consistency rules. For example, the SDMX DSD must have the AttributeRelationship for the DataAttributes, which does not exist in VTL.
++As said, the resulting [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definitions must be compliant with the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] consistency rules. For example, the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[DSD>>doc:sdmx:Glossary.Data structure definition.WebHome]] must have the AttributeRelationship for the DataAttributes, which does not exist in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]].
  ==== 12.3.4.2 Unpivot Mapping ====
--An alternative mapping method from VTL to SDMX is the **Unpivot **mapping.
++An alternative mapping method from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] is the **Unpivot **mapping.
--Although this mapping method can be used in any case, it makes major sense in case the VTL data structure has more than one measure component (multi-measures VTL structure). This is used to support the SDMX 2.1 case of a MeasureDimension or any other Dimension acting as a list of Measures, under the assumptions explained in section “Pivot Mapping”.
++Although this mapping method can be used in any case, it makes major sense in case the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data structure has more than one [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]] (multi-[[measures>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structure). This is used to support the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 case of a MeasureDimension or any other [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] acting as a list of [[Measures>>doc:sdmx:Glossary.Measure.WebHome]], under the assumptions explained in section “Pivot Mapping”.
--The multi-measures VTL structures are converted to SDMX Dataflows having an added MeasureDimension, which disambiguates the VTL multiple Measures, and a new Measure in place of the VTL ones, containing the values of the VTL Measures.
++The multi-[[measures>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures are converted to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]] having an added MeasureDimension, which disambiguates the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] multiple [[Measures>>doc:sdmx:Glossary.Measure.WebHome]], and a new [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] in place of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] ones, containing the values of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:sdmx:Glossary.Measure.WebHome]].
  The **unpivot** mapping behaves like follows:
--* like in the basic mapping, a VTL (simple) identifier becomes a SDMX Dimension and a VTL (time) identifier becomes a SDMX TimeDimension (as said, a measure identifier cannot exist in multi-measure VTL structures);
--* a MeasureDimension component called "measure_name" is added to the SDMX DataStructure;
--* a Measure component called "obs_value" is added to the SDMX DataStructure;
--* each VTL Measure is mapped to a Code of the SDMX MeasureDimension having the same name as the VTL Measure (therefore all the VTL Measure Components do not originate Components in the SDMX DataStructure);
--* a VTL Attribute becomes a SDMX DataAttribute having AttributeRelationship referred to all the SDMX DimensionComponents including the TimeDimension and except the MeasureDimension.
++* like in the basic mapping, a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (simple) identifier becomes a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] and a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (time) identifier becomes a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] TimeDimension (as said, a [[measure>>doc:sdmx:Glossary.Measure.WebHome]] identifier cannot exist in multi-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures);
++* a MeasureDimension [[component>>doc:sdmx:Glossary.Component.WebHome]] called "measure_name" is added to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure;
++* a [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]] called "obs_value" is added to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure;
++* each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] is (% style="color:#e74c3c" %)mapped(%%) to a [[Code>>doc:sdmx:Glossary.Code.WebHome]] of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension having the same name as the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] (therefore all the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[Components>>doc:sdmx:Glossary.Component.WebHome]] do not originate [[Components>>doc:sdmx:Glossary.Component.WebHome]] in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure);
++* a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] becomes a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute having AttributeRelationship referred to all the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponents including the TimeDimension and except the MeasureDimension.
  The summary mapping table of the **unpivot** mapping method is the following:
--|**VTL**|**SDMX**
--|(Simple) Identifier|Dimension
--|(Time) Identifier|TimeDimension
--|All Measure Components|MeasureDimension (having one Code for each VTL measure component) & one Measure
--|Attribute|DataAttribute depending on all SDMX Dimensions including the TimeDimension and except the MeasureDimension
++(% style="width:638.294px" %)
++|(% style="width:200px" %)**[[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]**|(% style="width:435px" %)**[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]**
++|(% style="width:200px" %)(Simple) Identifier|(% style="width:435px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]
++|(% style="width:200px" %)(Time) Identifier|(% style="width:435px" %)TimeDimension
++|(% style="width:200px" %)All [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[Components>>doc:sdmx:Glossary.Component.WebHome]]|(% style="width:435px" %)MeasureDimension (having one [[Code>>doc:sdmx:Glossary.Code.WebHome]] for each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]]) & one [[Measure>>doc:sdmx:Glossary.Measure.WebHome]]
++|(% style="width:200px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]|(% style="width:435px" %)DataAttribute depending on all [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] including the TimeDimension and except the MeasureDimension
--At observation / data point level:
++At observation / data point (% style="color:#e74c3c" %)level(%%):
--* a multi-measure VTL Data Point becomes a set of SDMX observations, one for each VTL Measure;
--* the values of the VTL Identifiers become the values of the corresponding SDMX DimensionComponents, for all the observations of the set above;
--* the name of the j^^th^^ VTL Measure (e.g. “Cj”) becomes the Code of the SDMX MeasureDimension of the j^^th^^ observation of the set;
--* the value of the j^^th^^ VTL Measure becomes the value of the SDMX Measure of the j^^th^^ observation of the set;
--* the values of the VTL Attributes become the values of the corresponding SDMX DataAttributes (in principle for all the observations of the set above).
++* a multi-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Data Point becomes a set of [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] observations, one for each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]];
++* the values of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Identifiers become the values of the corresponding [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponents, for all the observations of the set above;
++* the name of the j^^th^^ [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] (e.g. “Cj”) becomes the [[Code>>doc:sdmx:Glossary.Code.WebHome]] of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension of the j^^th^^ observation of the set;
++* the value of the j^^th^^ [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] becomes the value of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] of the j^^th^^ observation of the set;
++* the values of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]] become the values of the corresponding [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes (in principle for all the observations of the set above).
--If desired, this method can be applied also to mono-measure VTL structures, provided that none of the VTL Components has already the role of Measure Identifier. Like in the general case, a MeasureDimension component called “measure_name” is added to the SDMX DataStructure, in this case it has just one possible Code, corresponding to the name of the unique VTL Measure. The original VTL Measure would not become a Component in the SDMX data structure. The value of the VTL Measure would be assigned to the unique SDMX Measure called “obs_value”.
++If desired, this method can be applied also to mono-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures, provided that none of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Components>>doc:sdmx:Glossary.Component.WebHome]] has already the role of [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] Identifier. Like in the general case, a MeasureDimension [[component>>doc:sdmx:Glossary.Component.WebHome]] called “measure_name” is added to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure, in this case it has just one possible [[Code>>doc:sdmx:Glossary.Code.WebHome]], corresponding to the name of the unique [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]]. The original [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] would not become a [[Component>>doc:sdmx:Glossary.Component.WebHome]] in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data structure. The value of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] would be assigned to the unique [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] called “obs_value”.
--In any case, the resulting SDMX definitions must be compliant with the SDMX consistency rules. For example, the possible Codes of the SDMX MeasureDimension need to be listed in a SDMX Codelist, with proper id, agency and version; moreover, the SDMX DSD must have the AttributeRelationship for the DataAttributes, which does not exist in VTL.
++In any case, the resulting [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definitions must be compliant with the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] consistency rules. For example, the possible [[Codes>>doc:sdmx:Glossary.Code.WebHome]] of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension need to be listed in a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Codelist, with proper id, agency and (% style="color:#e74c3c" %)version(%%); moreover, the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[DSD>>doc:sdmx:Glossary.Data structure definition.WebHome]] must have the AttributeRelationship for the DataAttributes, which does not exist in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]].
  ==== 12.3.4.3 From VTL Measures to SDMX Data Attributes ====
--More than all for the multi-measure VTL structures (having more than one Measure Component), it may happen that the Measures of the VTL Data Structure need to be managed as DataAttributes in SDMX. Therefore, a third mapping method consists in transforming some VTL measures in a corresponding SDMX Measures and all the other VTL Measures in SDMX DataAttributes. This method is called M2A (“M2A” stands for “Measures to DataAttributes”).
++More than all for the multi-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures (having more than one [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[Component>>doc:sdmx:Glossary.Component.WebHome]]), it may happen that the [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Data Structure need to be managed as DataAttributes in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]. Therefore, a third mapping method consists in transforming some [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[measures>>doc:sdmx:Glossary.Measure.WebHome]] in a corresponding [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] and all the other [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes. This method is called M2A (“M2A” stands for “[[Measures>>doc:sdmx:Glossary.Measure.WebHome]] to DataAttributes”).
--All VTL Measures maintain their names in SDMX. The VTL Measure Components that become SDMX DataAttributes are the ones declared as DataAttributes in the target SDMX data structure definition.
++All [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] maintain their names in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]. The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[Components>>doc:sdmx:Glossary.Component.WebHome]] that become [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes are the ones declared as DataAttributes in the target [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data structure definition.
  The mapping table is the following:
--|VTL|SDMX
--|(Simple) Identifier|Dimension
--|(Time) Identifier|TimeDimension
--|Some Measures|Measure
--|Other Measures|DataAttribute
--|Attribute|DataAttribute
++(% style="width:467.294px" %)
++|(% style="width:214px" %)[[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]|(% style="width:250px" %)[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]
++|(% style="width:214px" %)(Simple) Identifier|(% style="width:250px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]
++|(% style="width:214px" %)(Time) Identifier|(% style="width:250px" %)TimeDimension
++|(% style="width:214px" %)Some [[Measures>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:250px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]
++|(% style="width:214px" %)Other [[Measures>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:250px" %)DataAttribute
++|(% style="width:214px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]|(% style="width:250px" %)DataAttribute
--Even in this case, the resulting SDMX definitions must be compliant with the SDMX consistency rules. For example, the SDMX DSD must have the attributeRelationship for the DataAttributes, which does not exist in VTL.
++Even in this case, the resulting [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] definitions must be compliant with the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] consistency rules. For example, the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[DSD>>doc:sdmx:Glossary.Data structure definition.WebHome]] must have the attributeRelationship for the DataAttributes, which does not exist in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]].
  === 12.3.5 Declaration of the mapping methods between data structures ===
--In order to define and understand properly VTL Transformations, the applied mapping methods must be specified in the SDMX structural metadata. If the default mapping method (Basic) is applied, no specification is needed.
++In order to define and understand properly [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations, the applied mapping methods must be specified in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[structural metadata>>doc:sdmx:Glossary.Structural metadata.WebHome]]. If the default mapping method (Basic) is applied, no specification is needed.
--A customized mapping can be defined through the VtlMappingScheme and VtlDataflowMapping classes (see the section of the SDMX IM relevant to the VTL). A VtlDataflowMapping allows specifying the mapping methods to be used for a specific dataflow, both in the direction from SDMX to VTL (toVtlMappingMethod) and from VTL to SDMX (fromVtlMappingMethod); in fact a VtlDataflowMapping associates the structured URN that identifies a SDMX Dataflow to its VTL alias and its mapping methods.
++A customized mapping can be defined through the VtlMappingScheme and VtlDataflowMapping classes (see the section of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] IM relevant to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]). A VtlDataflowMapping allows specifying the mapping methods to be used for a specific [[dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], both in the direction from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (toVtlMappingMethod) and from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (fromVtlMappingMethod); in fact a VtlDataflowMapping associates the structured URN that identifies a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] to its [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] alias and its mapping methods.
--It is possible to specify the toVtlMappingMethod and fromVtlMappingMethod also for the conventional dataflow called "generic_dataflow": in this case the specified mapping methods are intended to become the default ones, overriding the "Basic" methods. In turn, the toVtlMappingMethod and fromVtlMappingMethod declared for a specific Dataflow are intended to override the default ones for such a Dataflow.
++It is possible to specify the toVtlMappingMethod and fromVtlMappingMethod also for the conventional [[dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] called "generic_dataflow": in this case the specified mapping methods are intended to become the default ones, overriding the "Basic" methods. In turn, the toVtlMappingMethod and fromVtlMappingMethod declared for a specific [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] are intended to override the default ones for such a [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]].
--The VtlMappingScheme is a container for zero or more VtlDataflowMapping (it may contain also mappings towards artefacts other than dataflows).
++The VtlMappingScheme is a container for zero or more VtlDataflowMapping (it may contain also mappings towards [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] other than [[dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]]).
  === 12.3.6 Mapping dataflow subsets to distinct VTL Data Sets ===
--Until now it has been assumed to map one SMDX Dataflow to one VTL Data Set and vice-versa. This mapping one-to-one is not mandatory according to VTL because a VTL Data Set is meant to be a set of observations (data points) on a logical plane, having the same logical data structure and the same general meaning, independently of the possible physical representation or storage (see VTL 2.0 User Manual page 24), therefore a SDMX Dataflow can be seen either as a unique set of data observations (corresponding to one VTL Data Set) or as the union of many sets of data observations (each one corresponding to a distinct VTL Data Set).
++Until now it has been assumed to (% style="color:#e74c3c" %)map(%%) one SMDX [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] to one [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] and vice-versa. This mapping one-to-one is not mandatory according to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] because a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] is meant to be a set of observations (data points) on a logical plane, having the same logical data structure and the same general meaning, independently of the possible physical [[representation>>doc:sdmx:Glossary.Representation.WebHome]] or storage (see [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] 2.0 User Manual page 24), therefore a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] can be seen either as a unique set of data observations (corresponding to one [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]]) or as the union of many sets of data observations (each one corresponding to a distinct [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]]).
--As a matter of fact, in some cases it can be useful to define VTL operations involving definite parts of a SDMX Dataflow instead than the whole.{{footnote}}A typical example of this kind is the validation, and more in general the manipulation, of individual time series belonging to the same Dataflow, identifiable through the DimensionComponents of the Dataflow except the TimeDimension. The coding of these kind of operations might be simplified by mapping distinct time series (i.e. different parts of a SDMX Dataflow) to distinct VTL Data Sets.{{/footnote}}
++As a matter of fact, in some cases it can be useful to define [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operations involving definite parts of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] instead than the whole.{{footnote}}A typical example of this kind is the validation, and more in general the manipulation, of individual time series belonging to the same Dataflow, identifiable through the DimensionComponents of the Dataflow except the TimeDimension. The coding of these kind of operations might be simplified by mapping distinct time series (i.e. different parts of a SDMX Dataflow) to distinct VTL Data Sets.{{/footnote}}
--Therefore, in order to make the coding of VTL operations simpler when applied on parts of SDMX Dataflows, it is allowed to map distinct parts of a SDMX Dataflow to distinct VTL Data Sets according to the following rules and conventions. This kind of mapping is possible both from SDMX to VTL and from VTL to SDMX, as better explained below.{{footnote}}Please note that this kind of mapping is only an option at disposal of the definer of VTL Transformations; in fact it remains always possible to manipulate the needed parts of SDMX Dataflows by means of VTL operators (e.g. “sub”, “filter”, “calc”, “union” …), maintaining a mapping one-to-one between SDMX Dataflows and VTL Data Sets.{{/footnote}}
++Therefore, in order to make the coding of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operations simpler when applied on parts of [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]], it is allowed to (% style="color:#e74c3c" %)map(%%) distinct parts of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] to distinct [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] according to the following rules and conventions. This kind of mapping is possible both from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], as better explained below.{{footnote}}Please note that this kind of mapping is only an option at disposal of the definer of VTL Transformations; in fact it remains always possible to manipulate the needed parts of SDMX Dataflows by means of VTL operators (e.g. “sub”, “filter”, “calc”, “union” …), maintaining a mapping one-to-one between SDMX Dataflows and VTL Data Sets.{{/footnote}}
--Given a SDMX Dataflow and some predefined Dimensions of its DataStructure, it is allowed to map the subsets of observations that have the same combination of values for such Dimensions to correspondent VTL datasets.
++Given a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] and some predefined [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] of its DataStructure, it is allowed to (% style="color:#e74c3c" %)map(%%) the subsets of observations that have the same combination of values for such [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] to correspondent [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]].
--For example, assuming that the SDMX Dataflow DF1(1.0.0) has the Dimensions INDICATOR, TIME_PERIOD and COUNTRY, and that the user declares the Dimensions INDICATOR and COUNTRY as basis for the mapping (i.e. the mapping dimensions): the observations that have the same values for INDICATOR and COUNTRY would be mapped to the same VTL dataset (and vice-versa). In practice, this kind mapping is obtained like follows:
++For example, assuming that the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF1(1.0.0) has the [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] INDICATOR, TIME_PERIOD and COUNTRY, and that the user declares the [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY as basis for the mapping (i.e. the mapping [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]]): the observations that have the same values for INDICATOR and COUNTRY would be (% style="color:#e74c3c" %)mapped(%%) to the same [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] (and vice-versa). In practice, this kind mapping is obtained like follows:
--* For a given SDMX Dataflow, the user (VTL definer) declares the DimensionComponents on which the mapping will be based, in a given order.{{footnote}}This definition is made through the ToVtlSubspace and ToVtlSpaceKey classes and/or the FromVtlSuperspace and FromVtlSpaceKey classes, depending on the direction of the mapping (“key” means “dimension”). The mapping of Dataflow subsets can be applied independently in the two directions, also according to different Dimensions. When no Dimension is declared for a given direction, it is assumed that the option of mapping different parts of a SDMX Dataflow to different VTL Data Sets is not used.{{/footnote}} Following the example above, imagine that the user declares the Dimensions INDICATOR and COUNTRY.
--* The VTL Data Set is given a name using a special notation also called “ordered concatenation” and composed of the following parts:
--** The reference to the SDMX Dataflow (expressed according to the rules described in the previous paragraphs, i.e. URN, abbreviated URN or another alias); for example DF(1.0.0);
++* For a given [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], the user ([[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] definer) declares the DimensionComponents on which the mapping will be based, in a given order.{{footnote}}This definition is made through the ToVtlSubspace and ToVtlSpaceKey classes and/or the FromVtlSuperspace and FromVtlSpaceKey classes, depending on the direction of the mapping (“key” means “dimension”). The mapping of Dataflow subsets can be applied independently in the two directions, also according to different Dimensions. When no Dimension is declared for a given direction, it is assumed that the option of mapping different parts of a SDMX Dataflow to different VTL Data Sets is not used.{{/footnote}} Following the example above, imagine that the user declares the [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY.
++* The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] is given a name using a special notation also called “ordered concatenation” and composed of the following parts:
++** The reference to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] (expressed according to the rules described in the previous paragraphs, i.e. URN, abbreviated URN or another alias); for example DF(1.0.0);
  ** a slash (“/”) as a separator;{{footnote}}As a consequence of this formalism, a slash in the name of the VTL Data Set assumes the specific meaning of separator between the name of the Dataflow and the values of some of its Dimensions.{{/footnote}}
--** The reference to a specific part of the SDMX Dataflow above, expressed as the concatenation of the values that the SDMX DimensionComponents declared above must have, separated by dots (“.”) and written in the order in which these DimensionComponents are defined{{footnote}}This is the order in which the dimensions are defined in the ToVtlSpaceKey class or in the FromVtlSpaceKey class, depending on the direction of the mapping.{{/footnote}}. For example
++** The reference to a specific part of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] above, expressed as the concatenation of the values that the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponents declared above must have, separated by dots (“.”) and written in the order in which these DimensionComponents are defined{{footnote}}This is the order in which the dimensions are defined in the ToVtlSpaceKey class or in the FromVtlSpaceKey class, depending on the direction of the mapping.{{/footnote}}. For example
--POPULATION.USA would mean that such a VTL Data Set is mapped to the SDMX observations for which the dimension //INDICATOR// is equal to POPULATION and the dimension //COUNTRY// is equal to USA.
++POPULATION.USA would mean that such a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] is (% style="color:#e74c3c" %)mapped(%%) to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] observations for which the [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] //INDICATOR// is equal to POPULATION and the [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] //COUNTRY// is equal to USA.
--In the VTL Transformations, this kind of dataset name must be referenced between single quotes because the slash (“/”) is not a regular character according to the VTL rules.
++In the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations, this kind of [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] name must be referenced between single quotes because the slash (“/”) is not a regular character according to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] rules.
--Therefore, the generic name of this kind of VTL datasets would be:
++Therefore, the generic name of this kind of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] would be:
--'DF(1.0.0)/INDICATORvalue.COUNTRYvalue'
++> 'DF(1.0.0)/INDICATORvalue.COUNTRYvalue'
--Where DF(1.0.0) is the Dataflow and //INDICATORvalue// and //COUNTRYvalue //are placeholders for one value of the INDICATOR and COUNTRY dimensions. Instead the specific name of one of these VTL datasets would be:
++Where DF(1.0.0) is the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] and //INDICATORvalue// and //COUNTRYvalue //are placeholders for one value of the INDICATOR and COUNTRY [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]]. Instead the specific name of one of these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] would be:
--‘DF(1.0.0)/POPULATION.USA’
++> ‘DF(1.0.0)/POPULATION.USA’
--In particular, this is the VTL dataset that contains all the observations of the Dataflow DF(1.0.0) for which //INDICATOR// = POPULATION and //COUNTRY// = USA.
++In particular, this is the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] that contains all the observations of the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF(1.0.0) for which //INDICATOR// = POPULATION and //COUNTRY// = USA.
--Let us now analyse the different meaning of this kind of mapping in the two mapping directions, i.e. from SDMX to VTL and from VTL to SDMX.
++Let us now analyse the different meaning of this kind of mapping in the two mapping directions, i.e. from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]].
--As already said, the mapping from SDMX to VTL happens when the SDMX dataflows are operand of VTL Transformations, instead the mapping from VTL to SDMX happens when the VTL Data Sets that is result of Transformations{{footnote}}It should be remembered that, according to the VTL consistency rules, a given VTL dataset cannot be the result of more than one VTL Transformation.{{/footnote}} need to be treated as SDMX objects. This kind of mapping can be applied independently in the two directions and the Dimensions on which the mapping is based can be different in the two directions: these Dimensions are defined in the ToVtlSpaceKey and in the FromVtlSpaceKey classes respectively.
++As already said, the mapping from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] happens when the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]] are operand of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations, instead the mapping from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] happens when the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] that is result of Transformations{{footnote}}It should be remembered that, according to the VTL consistency rules, a given VTL dataset cannot be the result of more than one VTL Transformation.{{/footnote}} need to be treated as [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] objects. This kind of mapping can be applied independently in the two directions and the [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] on which the mapping is based can be different in the two directions: these [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] are defined in the ToVtlSpaceKey and in the FromVtlSpaceKey classes respectively.
--First, let us see what happens in the mapping direction from SDMX to VTL, i.e. when parts of a SDMX Dataflow (e.g. DF1(1.0.0)) need to be mapped to distinct VTL Data Sets that are operand of some VTL Transformations.
++First, let us see what happens in the mapping direction from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], i.e. when parts of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] (e.g. DF1(1.0.0)) need to be (% style="color:#e74c3c" %)mapped(%%) to distinct [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] that are operand of some [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations.
--As already said, each VTL Data Set is assumed to contain all the observations of the
++As already said, each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] is assumed to contain all the observations of the
--SDMX Dataflow having INDICATOR=//INDICATORvalue //and COUNTRY=// COUNTRYvalue//. For example, the VTL dataset ‘DF1(1.0.0)/POPULATION.USA’ would contain all the observations of DF1(1.0.0) having INDICATOR = POPULATION and COUNTRY = USA.
++[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] having INDICATOR=//INDICATORvalue //and COUNTRY=// COUNTRYvalue//. For example, the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] ‘DF1(1.0.0)/POPULATION.USA’ would contain all the observations of DF1(1.0.0) having INDICATOR = POPULATION and COUNTRY = USA.
--In order to obtain the data structure of these VTL Data Sets from the SDMX one, it is assumed that the SDMX DimensionComponents on which the mapping is based are dropped, i.e. not maintained in the VTL data structure; this is possible because their values are fixed for each one of the invoked VTL Data Sets{{footnote}}If these DimensionComponents would not be dropped, the various VTL Data Sets resulting from this kind of mapping would have non-matching values for the Identifiers corresponding to the mapping Dimensions (e.g. POPULATION and COUNTRY). As a consequence, taking into account that the typical binary VTL operations at dataset level (+, -, *, / and so on) are executed on the observations having matching values for the identifiers, it would not be possible to compose the resulting VTL datasets one another (e.g. it would not be possible to calculate the population ratio between USA and CANADA).{{/footnote}}. After that, the mapping method from SDMX to VTL specified for the Dataflow DF1(1.0.0) is applied (i.e.
++In order to obtain the data structure of these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] from the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] one, it is assumed that the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponents on which the mapping is based are dropped, i.e. not maintained in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data structure; this is possible because their values are fixed for each one of the invoked [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]]{{footnote}}If these DimensionComponents would not be dropped, the various VTL Data Sets resulting from this kind of mapping would have non-matching values for the Identifiers corresponding to the mapping Dimensions (e.g. POPULATION and COUNTRY). As a consequence, taking into account that the typical binary VTL operations at dataset level (+, -, *, / and so on) are executed on the observations having matching values for the identifiers, it would not be possible to compose the resulting VTL datasets one another (e.g. it would not be possible to calculate the population ratio between USA and CANADA).{{/footnote}}. After that, the mapping method from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] specified for the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF1(1.0.0) is applied (i.e. basic, pivot …).
--basic, pivot …).
++In the example above, for all the [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] of the kind
--In the example above, for all the datasets of the kind
++> ‘DF1(1.0.0)///INDICATORvalue//.//COUNTRYvalue//’, the dimensions INDICATOR and COUNTRY would be dropped so that the data structure of all the resulting VTL Data Sets would have the identifier TIME_PERIOD only.
--‘DF1(1.0.0)///INDICATORvalue//.//COUNTRYvalue//’, the dimensions INDICATOR and COUNTRY would be dropped so that the data structure of all the resulting VTL Data Sets would have the identifier TIME_PERIOD only.
++It should be noted that the desired [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] (i.e. of the kind ‘DF1(1.0.0)/// INDICATORvalue//.//COUNTRYvalue//’) can be obtained also by applying the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operator “**sub**” (subspace) to the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF1(1.0.0), like in the following [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] expression:
--It should be noted that the desired VTL Data Sets (i.e. of the kind ‘DF1(1.0.0)/// INDICATORvalue//.//COUNTRYvalue//’) can be obtained also by applying the VTL operator “**sub**” (subspace) to the Dataflow DF1(1.0.0), like in the following VTL expression:
++> ‘DF1(1.0.0)/POPULATION.USA’ :=
++> DF1(1.0.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“USA” ];
++>
++> ‘DF1(1.0.0)/POPULATION.CANADA’ :=
++> DF1(1.0.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“CANADA” ];
++>
++> … … …
--‘DF1(1.0.0)/POPULATION.USA’ :=
++In fact the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operator “sub” has exactly the same behaviour. Therefore, (% style="color:#e74c3c" %)mapping(%%) different parts of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] to different [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] in the direction from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] through the ordered concatenation notation is equivalent to a proper use of the operator “**sub**” on such a [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]].{{footnote}}In case the ordered concatenation notation is used, the VTL Transformation described above, e.g. ‘DF1(1.0)/POPULATION.USA’ := DF1(1.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“USA”], is implicitly executed. In order to test the overall compliance of the VTL program to the VTL consistency rules, it has to be considered as part of the VTL program even if it is not explicitly coded.{{/footnote}}
--DF1(1.0.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“USA” ];
++In the direction from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] it is allowed to omit the value of one or more DimensionComponents on which the (% style="color:#e74c3c" %)mapping(%%) is based, but maintaining all the separating dots (therefore it may happen to find two or more consecutive dots and dots in the beginning or in the end). The absence of value means that for the corresponding [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] all the values are kept and the [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] is not dropped.
--‘DF1(1.0.0)/POPULATION.CANADA’ :=
++For example, ‘DF(1.0.0)/POPULATION.’ (note the dot in the end of the name) is the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] that contains all the observations of the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF(1.0.0) for which //INDICATOR// = POPULATION and COUNTRY = any value.
--DF1(1.0.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“CANADA” ];
++This is equivalent to the application of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] “sub” operator only to the identifier //INDICATOR//:
--… … …
++> ‘DF1(1.0.0)/POPULATION.’ :=
++> DF1(1.0.0) [ sub INDICATOR=“POPULATION” ];
--In fact the VTL operator “sub” has exactly the same behaviour. Therefore, mapping different parts of a SDMX Dataflow to different VTL Data Sets in the direction from SDMX to VTL through the ordered concatenation notation is equivalent to a proper use of the operator “**sub**” on such a Dataflow.{{footnote}}In case the ordered concatenation notation is used, the VTL Transformation described above, e.g. ‘DF1(1.0)/POPULATION.USA’ := DF1(1.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“USA”], is implicitly executed. In order to test the overall compliance of the VTL program to the VTL consistency rules, it has to be considered as part of the VTL program even if it is not explicitly coded.{{/footnote}}
++Therefore the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] ‘DF1(1.0.0)/POPULATION.’ would have the identifiers COUNTRY and TIME_PERIOD.
--In the direction from SDMX to VTL it is allowed to omit the value of one or more DimensionComponents on which the mapping is based, but maintaining all the separating dots (therefore it may happen to find two or more consecutive dots and dots in the beginning or in the end). The absence of value means that for the corresponding Dimension all the values are kept and the Dimension is not dropped.
++Heterogeneous invocations of the same [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] are allowed, i.e. omitting different [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] in different invocations.
--For example, ‘DF(1.0.0)/POPULATION.’ (note the dot in the end of the name) is the VTL dataset that contains all the observations of the Dataflow DF(1.0.0) for which //INDICATOR// = POPULATION and COUNTRY = any value.
++Let us now analyse the (% style="color:#e74c3c" %)mapping(%%) direction from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]].
--This is equivalent to the application of the VTL “sub” operator only to the identifier //INDICATOR//:
++In this situation, distinct parts of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] are calculated as distinct [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]], under the (% style="color:#e74c3c" %)constraint(%%) that they must have the same [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data structure.
--‘DF1(1.0.0)/POPULATION.’ :=
++For example, let us assume that the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] programmer wants to calculate the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF2(1.0.0) having the [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] TIME_PERIOD, INDICATOR, and COUNTRY and that such a programmer finds it convenient to calculate separately the parts of DF2(1.0.0) that have different combinations of values for INDICATOR and COUNTRY:
--DF1(1.0.0) [ sub INDICATOR=“POPULATION” ];
++* each part is calculated as a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] derived [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]], result of a dedicated [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformation;{{footnote}}If the whole DF2(1.0) is calculated by means of just one VTL Transformation, then the mapping between the SDMX Dataflow and the corresponding VTL dataset is one-to-one and this kind of mapping (one SDMX Dataflow to many VTL datasets) does not apply.{{/footnote}}
++* the data structure of all these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] has the TIME_PERIOD identifier and does not have the INDICATOR and COUNTRY identifiers.{{footnote}}This is possible as each VTL dataset corresponds to one particular combination of values of INDICATOR and COUNTRY.{{/footnote}}
--Therefore the VTL Data Set ‘DF1(1.0.0)/POPULATION.’ would have the identifiers COUNTRY and TIME_PERIOD.
++Under these hypothesis, such derived [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] can be (% style="color:#e74c3c" %)mapped(%%) to DF2(1.0.0) by declaring the DimensionComponents INDICATOR and COUNTRY as (% style="color:#e74c3c" %)mapping(%%) [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]]{{footnote}}The mapping dimensions are defined as FromVtlSpaceKeys of the FromVtlSuperSpace of the VtlDataflowMapping relevant to DF2(1.0).{{/footnote}}.
--Heterogeneous invocations of the same Dataflow are allowed, i.e. omitting different Dimensions in different invocations.
++The corresponding [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations, assuming that the result needs to be persistent, would be of this kind
--Let us now analyse the mapping direction from VTL to SDMX.
++:{{footnote}}the symbol of the VTL persistent assignment is used (<-){{/footnote}}
--In this situation, distinct parts of a SDMX Dataflow are calculated as distinct VTL datasets, under the constraint that they must have the same VTL data structure.
++> ‘DF2(1.0.0)/INDICATORvalue.COUNTRYvalue’ <- expression
--For example, let us assume that the VTL programmer wants to calculate the SDMX Dataflow DF2(1.0.0) having the Dimensions TIME_PERIOD, INDICATOR, and COUNTRY and that such a programmer finds it convenient to calculate separately the parts of DF2(1.0.0) that have different combinations of values for INDICATOR and COUNTRY:
--
--* each part is calculated as a VTL derived Data Set, result of a dedicated VTL Transformation;{{footnote}}If the whole DF2(1.0) is calculated by means of just one VTL Transformation, then the mapping between the SDMX Dataflow and the corresponding VTL dataset is one-to-one and this kind of mapping (one SDMX Dataflow to many VTL datasets) does not apply.{{/footnote}}
--* the data structure of all these VTL Data Sets has the TIME_PERIOD identifier and does not have the INDICATOR and COUNTRY identifiers.{{footnote}}This is possible as each VTL dataset corresponds to one particular combination of values of INDICATOR and COUNTRY.{{/footnote}}
--
--Under these hypothesis, such derived VTL Data Sets can be mapped to DF2(1.0.0) by declaring the DimensionComponents INDICATOR and COUNTRY as mapping dimensions{{footnote}}The mapping dimensions are defined as FromVtlSpaceKeys of the FromVtlSuperSpace of the VtlDataflowMapping relevant to DF2(1.0).{{/footnote}}.
--
--The corresponding VTL Transformations, assuming that the result needs to be persistent, would be of this kind:{{footnote}}the symbol of the VTL persistent assignment is used (<-){{/footnote}}
--
--‘DF2(1.0.0)/INDICATORvalue.COUNTRYvalue’ <- expression
--
  Some examples follow, for some specific values of INDICATOR and COUNTRY:
--‘DF2(1.0.0)/GDPPERCAPITA.USA’ <- expression11; ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ <- expression12;
--… … …
++> ‘DF2(1.0.0)/GDPPERCAPITA.USA’ <- expression11; ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ <- expression12;
++> … … …
++> ‘DF2(1.0.0)/POPGROWTH.USA’ <- expression21;
++> ‘DF2(1.0.0)/POPGROWTH.CANADA’ <- expression22;
++> … … …
--‘DF2(1.0.0)/POPGROWTH.USA’  <- expression21;
--‘DF2(1.0.0)/POPGROWTH.CANADA’ <- expression22;
--… … …
++As said, it is assumed that these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] derived [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] have the TIME_PERIOD as the only identifier. In the mapping from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to SMDX, the [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY are added to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data structure on order to obtain the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] one, with the following values respectively:
--As said, it is assumed that these VTL derived Data Sets have the TIME_PERIOD as the only identifier. In the mapping from VTL to SMDX, the Dimensions INDICATOR and COUNTRY are added to the VTL data structure on order to obtain the SDMX one, with the following values respectively:
++> VTL dataset INDICATOR value COUNTRY value
++>
++> ‘DF2(1.0.0)/GDPPERCAPITA.USA’ GDPPERCAPITA USA
++> ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ GDPPERCAPITA CANADA … … …
++>
++> ‘DF2(1.0.0)/POPGROWTH.USA’ POPGROWTH USA
++> ‘DF2(1.0.0)/POPGROWTH.CANADA’ POPGROWTH CANADA
++> … … …
--VTL dataset   INDICATOR value COUNTRY value
++It should be noted that the application of this many-to-one mapping from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] is equivalent to an appropriate sequence of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations. These use the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operator “calc” to add the proper [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] identifiers (in the example, INDICATOR and COUNTRY) and to assign to them the proper values and the operator “union” in order to obtain the final [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] (in the example DF2(1.0.0)), that can be (% style="color:#e74c3c" %)mapped(%%) oneto-one to the homonymous [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]]. Following the same example, these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations would be:
--‘DF2(1.0.0)/GDPPERCAPITA.USA’  GDPPERCAPITA USA
--‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ GDPPERCAPITA CANADA … … …
--‘DF2(1.0.0)/POPGROWTH.USA’  POPGROWTH USA
--‘DF2(1.0.0)/POPGROWTH.CANADA’  POPGROWTH CANADA
++> DF2bis_GDPPERCAPITA_USA := ‘DF2(1.0.0)/GDPPERCAPITA.USA’ [calc identifier INDICATOR := ”GDPPERCAPITA”, identifier COUNTRY := ”USA”]; DF2bis_GDPPERCAPITA_CANADA := ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ [calc identifier INDICATOR:=”GDPPERCAPITA”, identifier COUNTRY:=”CANADA”];… … … DF2bis_POPGROWTH_USA := ‘DF2(1.0.0)/POPGROWTH.USA’ [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”USA”]; DF2bis_POPGROWTH_CANADA’ := ‘DF2(1.0.0)/POPGROWTH.CANADA’ [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”CANADA”];… … … DF2(1.0) <- UNION (DF2bis_GDPPERCAPITA_USA’, DF2bis_GDPPERCAPITA_CANADA’,
++> … ,
++> DF2bis_POPGROWTH_USA’, DF2bis_POPGROWTH_CANADA’
++> …);
--… … …
++In other words, starting from the [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] explicitly calculated through [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] (in the example ‘DF2(1.0)/GDPPERCAPITA.USA’ and so on), the first step consists in calculating other (non-persistent) [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] (in the example DF2bis_GDPPERCAPITA_USA and so on) by adding the identifiers INDICATOR and COUNTRY with the desired values (//INDICATORvalue// and //COUNTRYvalue)//. Finally, all these non-persistent [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] are united and give the final result DF2(1.0){{footnote}}The result is persistent in this example but it can be also non persistent if needed.{{/footnote}}, which can be (% style="color:#e74c3c" %)mapped(%%) one-to-one to the homonymous [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] having the [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] [[components>>doc:sdmx:Glossary.Component.WebHome]] TIME_PERIOD, INDICATOR and COUNTRY.
--It should be noted that the application of this many-to-one mapping from VTL to SDMX is equivalent to an appropriate sequence of VTL Transformations. These use the VTL operator “calc” to add the proper VTL identifiers (in the example, INDICATOR and COUNTRY) and to assign to them the proper values and the operator “union” in order to obtain the final VTL dataset (in the example DF2(1.0.0)), that can be mapped oneto-one to the homonymous SDMX Dataflow. Following the same example, these VTL Transformations would be:
++Therefore, (% style="color:#e74c3c" %)mapping(%%) different [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] having the same data structure to different parts of a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], i.e. in the direction from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], through the ordered concatenation notation is equivalent to a proper use of the operators “calc” and “union” on such [[datasets>>doc:sdmx:Glossary.Data set.WebHome]].{{footnote}}In case the ordered concatenation notation from VTL to SDMX is used, the set of Transformations described above is implicitly performed; therefore, in order to test the overall compliance of the VTL program to the VTL consistency rules, these implicit Transformations have to be considered as part of the VTL program even if they are not explicitly coded.{{/footnote}}{{footnote}}Through SDMX Constraints, it is possible to specify the values that a Component of a Dataflow can assume.{{/footnote}}
--DF2bis_GDPPERCAPITA_USA := ‘DF2(1.0.0)/GDPPERCAPITA.USA’ [calc identifier INDICATOR := ”GDPPERCAPITA”, identifier COUNTRY := ”USA”];
--DF2bis_GDPPERCAPITA_CANADA := ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ [calc identifier INDICATOR:=”GDPPERCAPITA”, identifier COUNTRY:=”CANADA”]; … … …
--DF2bis_POPGROWTH_USA  := ‘DF2(1.0.0)/POPGROWTH.USA’
--[calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”USA”];
--DF2bis_POPGROWTH_CANADA’ := ‘DF2(1.0.0)/POPGROWTH.CANADA’ [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”CANADA”]; … … …
--DF2(1.0) <- UNION   (DF2bis_GDPPERCAPITA_USA’,
--DF2bis_GDPPERCAPITA_CANADA’,
--… ,
--DF2bis_POPGROWTH_USA’,
--DF2bis_POPGROWTH_CANADA’
--…);
++It is worth noting that in the direction from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] it is mandatory to specify the value for every [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] on which the (% style="color:#e74c3c" %)mapping(%%) is based (in other word, in the name of the calculated [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] is not possible to omit the value of some of the Dimensions).
--In other words, starting from the datasets explicitly calculated through VTL (in the example ‘DF2(1.0)/GDPPERCAPITA.USA’ and so on), the first step consists in calculating other (non-persistent) VTL datasets (in the example DF2bis_GDPPERCAPITA_USA and so on) by adding the identifiers INDICATOR and COUNTRY with the desired values (//INDICATORvalue// and //COUNTRYvalue)//. Finally, all these non-persistent Data Sets are united and give the final result DF2(1.0){{footnote}}The result is persistent in this example but it can be also non persistent if needed.{{/footnote}}, which can be mapped one-to-one to the homonymous SDMX Dataflow having the dimension components TIME_PERIOD, INDICATOR and COUNTRY.
--
--Therefore, mapping different VTL datasets having the same data structure to different parts of a SDMX Dataflow, i.e. in the direction from VTL to SDMX, through the ordered concatenation notation is equivalent to a proper use of the operators “calc” and “union” on such datasets.{{footnote}}In case the ordered concatenation notation from VTL to SDMX is used, the set of Transformations described above is implicitly performed; therefore, in order to test the overall compliance of the VTL program to the VTL consistency rules, these implicit Transformations have to be considered as part of the VTL program even if they are not explicitly coded.{{/footnote}}{{footnote}}Through SDMX Constraints, it is possible to specify the values that a Component of a Dataflow can assume.{{/footnote}}
--
--It is worth noting that in the direction from VTL to SDMX it is mandatory to specify the value for every Dimension on which the mapping is based (in other word, in the name of the calculated VTL dataset is not possible to omit the value of some of the Dimensions).
--
  === 12.3.7 Mapping variables and value domains between VTL and SDMX ===
--With reference to the VTL “model for Variables and Value domains”, the following additional mappings have to be considered:
++With reference to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] “model for Variables and Value domains”, the following additional mappings have to be considered:
--|VTL|SDMX
--|**Data Set Component**|Although this abstraction exists in SDMX, it does not have an explicit definition and correspond to a Component (either a DimensionComponent or a Measure or a DataAttribute) belonging to one specific Dataflow^^43^^
--|**Represented Variable**|**Concept** with a definite Representation
--|**Value Domain**|(((
--**Representation** (see the Structure
++(% style="width:706.294px" %)
++|(% style="width:257px" %)[[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]|(% style="width:446px" %)[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]
++|(% style="width:257px" %)**[[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] [[Component>>doc:sdmx:Glossary.Component.WebHome]]**|(% style="width:446px" %)Although this abstraction exists in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], it does not have an explicit definition and correspond to a [[Component>>doc:sdmx:Glossary.Component.WebHome]] (either a DimensionComponent or a [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] or a DataAttribute) belonging to one specific [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]]^^43^^
++|(% style="width:257px" %)**Represented Variable**|(% style="width:446px" %)(% style="color:#e74c3c" %)**Concept**(%%) with a definite [[Representation>>doc:sdmx:Glossary.Representation.WebHome]]
++|(% style="width:257px" %)**Value Domain**|(% style="width:446px" %)(((
++**[[Representation>>doc:sdmx:Glossary.Representation.WebHome]]** (see the Structure
  Pattern in the Base Package)
  )))
--|**Enumerated Value Domain / Code List**|**Codelist**
--|**Code**|**Code** (for enumerated DimensionComponent, Measure, DataAttribute)
--|**Described Value Domain**|(((
--non-enumerated** Representation**
--(having Facets / ExtendedFacets, see the Structure Pattern in the Base Package)
++|(% style="width:257px" %)**Enumerated Value Domain / [[Code List>>doc:sdmx:Glossary.Code list.WebHome]]**|(% style="width:446px" %)**Codelist**
++|(% style="width:257px" %)**[[Code>>doc:sdmx:Glossary.Code.WebHome]]**|(% style="width:446px" %)**[[Code>>doc:sdmx:Glossary.Code.WebHome]]** (for enumerated DimensionComponent, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]], DataAttribute)
++|(% style="width:257px" %)**Described Value Domain**|(% style="width:446px" %)(((
++non-enumerated** [[Representation>>doc:sdmx:Glossary.Representation.WebHome]]**
++(having [[Facets>>doc:sdmx:Glossary.Facet.WebHome]] / ExtendedFacets, see the Structure Pattern in the Base Package)
  )))
--|**Value**|Although this abstraction exists in SDMX, it does not have an explicit definition and correspond to a **Code** of a Codelist (for enumerated Representations) or
--| |to a valid **value **(for non-enumerated** **Representations)
--|**Value Domain Subset / Set**|This abstraction does not exist in SDMX
--|**Enumerated Value Domain Subset / Enumerated Set**|This abstraction does not exist in SDMX
--|**Described Value Domain Subset / Described Set**|This abstraction does not exist in SDMX
--|**Set list**|This abstraction does not exist in SDMX
++|(% style="width:257px" %)**Value**|(% style="width:446px" %)Although this abstraction exists in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], it does not have an explicit definition and correspond to a **[[Code>>doc:sdmx:Glossary.Code.WebHome]]** of a Codelist (for enumerated [[Representations>>doc:sdmx:Glossary.Representation.WebHome]]) or
++|(% style="width:257px" %) |(% style="width:446px" %)to a valid **value **(for non-enumerated** **[[Representations>>doc:sdmx:Glossary.Representation.WebHome]])
++|(% style="width:257px" %)**Value Domain Subset / Set**|(% style="width:446px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]
++|(% style="width:257px" %)**Enumerated Value Domain Subset / Enumerated Set**|(% style="width:446px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]
++|(% style="width:257px" %)**Described Value Domain Subset / Described Set**|(% style="width:446px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]
++|(% style="width:257px" %)**Set list**|(% style="width:446px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]
--The main difference between VTL and SDMX relies on the fact that the VTL artefacts for defining subsets of Value Domains do not exist in SDMX, therefore the VTL features for referring to predefined subsets are not available in SDMX. These artefacts are the Value Domain Subset (or Set), either enumerated or described, the Set List (list of values belonging to enumerated subsets) and the Data Set Component (aimed at defining the set of values that the Component of a Data Set can take, possibly a subset of the codes of Value Domain).
++The main difference between [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] relies on the fact that the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] for defining subsets of Value Domains do not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], therefore the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] features for referring to predefined subsets are not available in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]. These [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] are the Value Domain Subset (or Set), either enumerated or described, the Set List (list of values belonging to enumerated subsets) and the [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] [[Component>>doc:sdmx:Glossary.Component.WebHome]] (aimed at defining the set of values that the [[Component>>doc:sdmx:Glossary.Component.WebHome]] of a [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] can take, possibly a subset of the [[codes>>doc:sdmx:Glossary.Code.WebHome]] of Value Domain).
--Another difference consists in the fact that all Value Domains are considered as identifiable objects in VTL either if enumerated or not, while in SDMX the Codelist (corresponding to a VTL enumerated Value Domain) is identifiable, while the SDMX non-enumerated Representation (corresponding to a VTL non-enumerated Value Domain) is not identifiable. As a consequence, the definition of the VTL Rulesets, which in VTL can refer either to enumerated or non-enumerated value domains, in SDMX can refer only to enumerated Value Domains (i.e. to SDMX Codelists). As for the mapping between VTL variables and SDMX Concepts, it should be noted that these artefacts do not coincide perfectly. In fact, the VTL variables are represented variables, defined always on the same Value Domain (“Representation” in SDMX) independently of the data set / data structure in which they appear{{footnote}}By using represented variables, VTL can assume that data structures having the same variables as identifiers can be composed one another because the correspondent values can match.{{/footnote}}, while the SDMX Concepts can have different Representations in different DataStructures.{{footnote}}A Concept becomes a Component in a DataStructureDefinition, and Components can have different LocalRepresentations in different DataStructureDefinitions, also overriding the (possible) base representation of the Concept.{{/footnote}} This means that one SDMX Concept can correspond to many VTL Variables, one for each representation the Concept has.
++Another difference consists in the fact that all Value Domains are considered as identifiable objects in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] either if enumerated or not, while in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] the Codelist (corresponding to a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] enumerated Value Domain) is identifiable, while the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] non-enumerated [[Representation>>doc:sdmx:Glossary.Representation.WebHome]] (corresponding to a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] non-enumerated Value Domain) is not identifiable. As a consequence, the definition of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Rulesets, which in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] can refer either to enumerated or non-enumerated value domains, in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] can refer only to enumerated Value Domains (i.e. to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Codelists). As for the (% style="color:#e74c3c" %)mapping(%%) between [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] variables and [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (% style="color:#e74c3c" %)Concepts(%%), it should be noted that these [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] do not coincide perfectly. In fact, the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] variables are represented variables, defined always on the same Value Domain (“[[Representation>>doc:sdmx:Glossary.Representation.WebHome]]” in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]) independently of the [[data set>>doc:sdmx:Glossary.Data set.WebHome]] / data structure in which they appear{{footnote}}By using represented variables, VTL can assume that data structures having the same variables as identifiers can be composed one another because the correspondent values can match.{{/footnote}}, while the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (% style="color:#e74c3c" %)Concepts(%%) can have different [[Representations>>doc:sdmx:Glossary.Representation.WebHome]] in different DataStructures.{{footnote}}A Concept becomes a Component in a DataStructureDefinition, and Components can have different LocalRepresentations in different DataStructureDefinitions, also overriding the (possible) base representation of the Concept.{{/footnote}} This means that one [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (% style="color:#e74c3c" %)Concept(%%) can correspond to many [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Variables, one for each [[representation>>doc:sdmx:Glossary.Representation.WebHome]] the (% style="color:#e74c3c" %)Concept(%%) has.
--Therefore, it is important to be aware that some VTL operations (for example the binary operations at data set level) are consistent only if the components having the same names in the operated VTL Data Sets have also the same representation (i.e. the same Value Domain as for VTL). For example, it is possible to obtain correct results from the VTL expression
++Therefore, it is important to be aware that some [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operations (for example the binary operations at [[data set>>doc:sdmx:Glossary.Data set.WebHome]] (% style="color:#e74c3c" %)level(%%)) are consistent only if the [[components>>doc:sdmx:Glossary.Component.WebHome]] having the same names in the operated [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]] have also the same [[representation>>doc:sdmx:Glossary.Representation.WebHome]] (i.e. the same Value Domain as for [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]). For example, it is possible to obtain correct results from the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] expression
--DS_c := DS_a + DS_b (where DS_a, DS_b, DS_c are VTL Data Sets) if the matching components in DS_a and DS_b (e.g. ref_date, geo_area, sector …) refer to the same general representation. In simpler words, DS_a and DS_b must use the same values/codes (for ref_date, geo_area, sector … ), otherwise the relevant values would not match and the result of the operation would be wrong.
++> DS_c := DS_a + DS_b (where DS_a, DS_b, DS_c are VTL Data Sets)
--As mentioned, the property above is not enforced by construction in SDMX, and different representations of the same Concept can be not compatible one another (for example, it may happen that geo_area is represented by ISO-alpha-3 codes in DS_a and by ISO alpha-2 codes in DS_b). Therefore, it will be up to the definer of VTL
++if the matching [[components>>doc:sdmx:Glossary.Component.WebHome]] in DS_a and DS_b (e.g. ref_date, geo_area, sector …) refer to the same general [[representation>>doc:sdmx:Glossary.Representation.WebHome]]. In simpler words, DS_a and DS_b must use the same values/[[codes>>doc:sdmx:Glossary.Code.WebHome]] (for ref_date, geo_area, sector … ), otherwise the relevant values would not match and the result of the operation would be wrong.
--Transformations to ensure that the VTL expressions are consistent with the actual representations of the correspondent SDMX Concepts.
++As mentioned, the property above is not enforced by construction in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], and different [[representations>>doc:sdmx:Glossary.Representation.WebHome]] of the same (% style="color:#e74c3c" %)Concept(%%) can be not compatible one another (for example, it may happen that geo_area is represented by ISO-alpha-3 [[codes>>doc:sdmx:Glossary.Code.WebHome]] in DS_a and by ISO alpha-2 [[codes>>doc:sdmx:Glossary.Code.WebHome]] in DS_b). Therefore, it will be up to the definer of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]
--It remains up to the SDMX-VTL definer also the assurance of the consistency between a VTL Ruleset defined on Variables and the SDMX Components on which the Ruleset is applied. In fact, a VTL Ruleset is expressed by means of the values of the Variables (i.e. SDMX Concepts), i.e. assuming definite representations for them (e.g. ISOalpha-3 for country). If the Ruleset is applied to SDMX Components that have the same name of the Concept they refer to but different representations (e.g. ISO-alpha-2 for country), the Ruleset cannot work properly.
++Transformations to ensure that the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] expressions are consistent with the actual [[representations>>doc:sdmx:Glossary.Representation.WebHome]] of the correspondent [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (% style="color:#e74c3c" %)Concepts(%%).
++It remains up to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]-[[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] definer also the assurance of the consistency between a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Ruleset defined on Variables and the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Components>>doc:sdmx:Glossary.Component.WebHome]] on which the Ruleset is applied. In fact, a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Ruleset is expressed by means of the values of the Variables (i.e. [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] (% style="color:#e74c3c" %)Concepts(%%)), i.e. assuming definite [[representations>>doc:sdmx:Glossary.Representation.WebHome]] for them (e.g. ISOalpha-3 for country). If the Ruleset is applied to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Components>>doc:sdmx:Glossary.Component.WebHome]] that have the same name of the (% style="color:#e74c3c" %)Concept(%%) they refer to but different [[representations>>doc:sdmx:Glossary.Representation.WebHome]] (e.g. ISO-alpha-2 for country), the Ruleset cannot work properly.
++
  == 12.4 Mapping between SDMX and VTL Data Types ==
  === 12.4.1 VTL Data types ===
--According to the VTL User Guide the possible operations in VTL depend on the data types of the artefacts. For example, numbers can be multiplied but text strings cannot. In the VTL Transformations, the compliance between the operators and the data types of their operands is statically checked, i.e., violations result in compile-time errors.
++According to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] User Guide the possible operations in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] depend on the data types of the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]]. For example, numbers can be multiplied but text strings cannot. In the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations, the compliance between the operators and the data types of their operands is statically checked, i.e., violations result in compile-time errors.
--The VTL data types are sub-divided in scalar types (like integers, strings, etc.), which are the types of the scalar values, and compound types (like Data Sets, Components, Rulesets, etc.), which are the types of the compound structures. See below the diagram of the VTL data types, taken from the VTL User Manual:
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data types are sub-divided in scalar types (like integers, strings, etc.), which are the types of the scalar values, and compound types (like [[Data Sets>>doc:sdmx:Glossary.Data set.WebHome]], [[Components>>doc:sdmx:Glossary.Component.WebHome]], Rulesets, etc.), which are the types of the compound structures. See below the diagram of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data types, taken from the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] User Manual:
--[[image:1750067055028-964.png]]
++[[image:1750070288958-132.png]]
  **Figure 22 – VTL Data Types**
--The VTL scalar types are in turn subdivided in basic scalar types, which are elementary (not defined in term of other data types) and Value Domain and Set scalar types, which are defined in terms of the basic scalar types.
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] scalar types are in turn subdivided in basic scalar types, which are elementary (not defined in term of other data types) and Value Domain and Set scalar types, which are defined in terms of the basic scalar types.
--The VTL basic scalar types are listed below and follow a hierarchical structure in terms of supersets/subsets (e.g. "scalar" is the superset of all the basic scalar types):
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar types are listed below and follow a hierarchical structure in terms of supersets/subsets (e.g. "scalar" is the superset of all the basic scalar types):
++[[image:1750070310572-584.png]]
++
  **Figure 23 – VTL Basic Scalar Types**
  === 12.4.2 VTL basic scalar types and SDMX data types ===
--The VTL assumes that a basic scalar type has a unique internal representation and can have more external representations.
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] assumes that a basic scalar type has a unique internal [[representation>>doc:sdmx:Glossary.Representation.WebHome]] and can have more external [[representations>>doc:sdmx:Glossary.Representation.WebHome]].
--The internal representation is the format used within a VTL system to represent (and process) all the scalar values of a certain type. In principle, this format is hidden and not necessarily known by users. The external representations are instead the external formats of the values of a certain basic scalar type, i.e. the formats known by the users. For example, the internal representation of the dates can be an integer counting the days since a predefined date (e.g. from 01/01/4713 BC up to 31/12/5874897 AD like in Postgres) while two possible external representations are the formats YYYY-MMGG and MM-GG-YYYY (e.g. respectively 2010-12-31 and 12-31-2010).
++The internal [[representation>>doc:sdmx:Glossary.Representation.WebHome]] is the format used within a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] system to represent (and process) all the scalar values of a certain type. In principle, this format is hidden and not necessarily known by users. The external [[representations>>doc:sdmx:Glossary.Representation.WebHome]] are instead the external formats of the values of a certain basic scalar type, i.e. the formats known by the users. For example, the internal [[representation>>doc:sdmx:Glossary.Representation.WebHome]] of the dates can be an integer counting the days since a predefined date (e.g. from 01/01/4713 BC up to 31/12/5874897 AD like in Postgres) while two possible external [[representations>>doc:sdmx:Glossary.Representation.WebHome]] are the formats YYYY-MMGG and MM-GG-YYYY (e.g. respectively 2010-12-31 and 12-31-2010).
--The internal representation is the reference format that allows VTL to operate on more values of the same type (for example on more dates) even if such values have different external formats: these values are all converted to the unique internal representation so that they can be composed together (e.g. to find the more recent date, to find the time span between these dates and so on).
++The internal [[representation>>doc:sdmx:Glossary.Representation.WebHome]] is the reference format that allows [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to operate on more values of the same type (for example on more dates) even if such values have different external formats: these values are all converted to the unique internal [[representation>>doc:sdmx:Glossary.Representation.WebHome]] so that they can be composed together (e.g. to find the more recent date, to find the time span between these dates and so on).
--The VTL assumes that a unique internal representation exists for each basic scalar type but does not prescribe any particular format for it, leaving the VTL systems free to using they preferred or already existing internal format. By consequence, in VTL the basic scalar types are abstractions not associated to a specific format.
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] assumes that a unique internal [[representation>>doc:sdmx:Glossary.Representation.WebHome]] exists for each basic scalar type but does not prescribe any particular format for it, leaving the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] systems free to using they preferred or already existing internal format. By consequence, in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] the basic scalar types are abstractions not associated to a specific format.
--SDMX data types are conceived instead to support the data exchange, therefore they do have a format, which is known by the users and correspond, in VTL terms, to external representations. Therefore, for each VTL basic scalar type there can be more SDMX data types (the latter are explained in the section "General Notes for Implementers" of this document and are actually much more numerous than the former).
++[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data types are conceived instead to support the data exchange, therefore they do have a format, which is known by the users and correspond, in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] terms, to external [[representations>>doc:sdmx:Glossary.Representation.WebHome]]. Therefore, for each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar type there can be more [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data types (the latter are explained in the section "General Notes for Implementers" of this document and are actually much more numerous than the former).
--The following paragraphs describe the mapping between the SDMX data types and the VTL basic scalar types. This mapping shall be presented in the two directions of possible conversion, i.e. from SDMX to VTL and vice-versa.
++The following paragraphs describe the mapping between the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data types and the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar types. This mapping shall be presented in the two directions of possible conversion, i.e. from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] and vice-versa.
--The conversion from SDMX to VTL happens when an SDMX artefact acts as inputs of a VTL Transformation. As already said, in fact, at compile time the VTL needs to know the VTL type of the operands in order to check their compliance with the VTL operators and at runtime it must convert the values from their external (SDMX) representations to the corresponding internal (VTL) ones.
++The conversion from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] happens when an [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] acts as inputs of a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformation. As already said, in fact, at compile time the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] needs to know the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] type of the operands in order to check their compliance with the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operators and at runtime it must convert the values from their external ([[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]) [[representations>>doc:sdmx:Glossary.Representation.WebHome]] to the corresponding internal ([[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]) ones.
--The opposite conversion, i.e. from VTL to SDMX, happens when a VTL result, i.e. a VTL Data Set output of a Transformation, must become a SDMX artefact (or part of it). The values of the VTL result must be converted into the desired (SDMX) external representations (data types) of the SDMX artefact.
++The opposite conversion, i.e. from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], happens when a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] result, i.e. a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] output of a Transformation, must become a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] (or part of it). The values of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] result must be converted into the desired ([[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]) external [[representations>>doc:sdmx:Glossary.Representation.WebHome]] (data types) of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]].
  === 12.4.3 Mapping SDMX data types to VTL basic scalar types ===
--The following table describes the default mapping for converting from the SDMX data types to the VTL basic scalar types.
++The following table describes the default mapping for converting from the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data types to the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar types.
--|SDMX data type (BasicComponentDataType)|Default VTL basic scalar type
--|(((
++(% style="width:583.294px" %)
++|(% style="width:360px" %)[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data type (BasicComponentDataType)|(% style="width:221px" %)Default [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar type
++|(% style="width:360px" %)(((
  String
  (string allowing any character)
--)))|string
--|(((
--Alpha
--
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
++Alpha
  (string which only allows A-z)
--)))|string
--|(((
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
  AlphaNumeric
  (string which only allows A-z and 0-9)
--)))|string
--|(((
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
  Numeric
--
  (string which only allows 0-9, but is not numeric so that is can having leading zeros)
--)))|string
--|(((
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
  BigInteger
  (corresponds to XML Schema xs:integer datatype; infinite set of integer values)
--)))|integer
--|(((
++)))|(% style="width:221px" %)integer
++|(% style="width:360px" %)(((
  Integer
  (corresponds to XML Schema xs:int datatype; between -2147483648 and +2147483647
  (inclusive))
--)))|integer
--|(((
++)))|(% style="width:221px" %)integer
++|(% style="width:360px" %)(((
  Long
  (corresponds to XML Schema xs:long datatype; between -9223372036854775808 and
  +9223372036854775807 (inclusive))
--)))|integer
--|(((
++)))|(% style="width:221px" %)integer
++|(% style="width:360px" %)(((
  Short
  (corresponds to XML Schema xs:short datatype; between -32768 and -32767 (inclusive))
--)))|integer
--|Decimal (corresponds to XML Schema xs:decimal datatype; subset of real numbers that can be represented as decimals)|number
--|(((
++)))|(% style="width:221px" %)integer
++|(% style="width:360px" %)[[Decimal>>doc:sdmx:Glossary.Decimals.WebHome]] (corresponds to XML Schema xs:[[decimal>>doc:sdmx:Glossary.Decimals.WebHome]] datatype; subset of real numbers that can be represented as [[decimals>>doc:sdmx:Glossary.Decimals.WebHome]])|(% style="width:221px" %)number
++|(% style="width:360px" %)(((
  Float
  (corresponds to XML Schema xs:float datatype; patterned after the IEEE single-precision 32-bit floating point type)
--)))|number
--|(((
++)))|(% style="width:221px" %)number
++|(% style="width:360px" %)(((
  Double
  (corresponds to XML Schema xs:double datatype; patterned after the IEEE double-precision 64-bit floating point type)
--)))|number
--|(((
++)))|(% style="width:221px" %)number
++|(% style="width:360px" %)(((
  Boolean
--(corresponds to the XML Schema xs:boolean datatype; support the mathematical concept of
++(corresponds to the XML Schema xs:boolean datatype; support the mathematical (% style="color:#e74c3c" %)concept(%%) of
  binary-valued logic: {true, false})
--)))|boolean
--|(((
++)))|(% style="width:221px" %)boolean
++|(% style="width:360px" %)(((
  URI
  (corresponds to the XML Schema xs:anyURI; absolute or relative Uniform Resource Identifier Reference)
--)))|string
--|(((
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
  Count
  (an integer following a sequential pattern, increasing by 1 for each occurrence)
--)))|integer
--|(((
++)))|(% style="width:221px" %)integer
++|(% style="width:360px" %)(((
  InclusiveValueRange
--(decimal number within a closed interval, whose bounds are specified in the SDMX representation by the facets minValue and maxValue)
--)))|number
--|(((
++([[decimal>>doc:sdmx:Glossary.Decimals.WebHome]] number within a closed interval, whose bounds are specified in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[representation>>doc:sdmx:Glossary.Representation.WebHome]] by the [[facets>>doc:sdmx:Glossary.Facet.WebHome]] minValue and maxValue)
++)))|(% style="width:221px" %)number
++|(% style="width:360px" %)(((
  ExclusiveValueRange
--(decimal number within an open interval, whose bounds are specified in the SDMX representation by the facets minValue and maxValue)
--)))|number
--|(((
++([[decimal>>doc:sdmx:Glossary.Decimals.WebHome]] number within an open interval, whose bounds are specified in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[representation>>doc:sdmx:Glossary.Representation.WebHome]] by the [[facets>>doc:sdmx:Glossary.Facet.WebHome]] minValue and maxValue)
++)))|(% style="width:221px" %)number
++|(% style="width:360px" %)(((
  Incremental
--(decimal number the increased by a specific interval (defined by the interval facet), which is typically enforced outside of the XML validation)
--)))|number
--|(((
++([[decimal>>doc:sdmx:Glossary.Decimals.WebHome]] number the increased by a specific interval (defined by the interval [[facet>>doc:sdmx:Glossary.Facet.WebHome]]), which is typically enforced outside of the XML validation)
++)))|(% style="width:221px" %)number
++|(% style="width:360px" %)(((
  ObservationalTimePeriod
  (superset of StandardTimePeriod and TimeRange)
--)))|time
--|(((
++)))|(% style="width:221px" %)time
++|(% style="width:360px" %)(((
  StandardTimePeriod
  (superset of BasicTimePeriod and ReportingTimePeriod)
--)))|time
--|(((
++)))|(% style="width:221px" %)time
++|(% style="width:360px" %)(((
  BasicTimePeriod
  (superset of GregorianTimePeriod and DateTime)
--)))|date
--|(((
++)))|(% style="width:221px" %)date
++|(% style="width:360px" %)(((
  GregorianTimePeriod
  (superset of GregorianYear, GregorianYearMonth, and GregorianDay)
--)))|date
--|GregorianYear  (YYYY)|date
--|GregorianYearMonth / GregorianMonth (YYYY-MM)|date
--|GregorianDay (YYYY-MM-DD)|date
--|(((
++)))|(% style="width:221px" %)date
++|(% style="width:360px" %)GregorianYear (YYYY)|(% style="width:221px" %)date
++|(% style="width:360px" %)GregorianYearMonth / GregorianMonth (YYYY-MM)|(% style="width:221px" %)date
++|(% style="width:360px" %)GregorianDay (YYYY-MM-DD)|(% style="width:221px" %)date
++|(% style="width:360px" %)(((
  ReportingTimePeriod
  (superset of RepostingYear, ReportingSemester, ReportingTrimester, ReportingQuarter, ReportingMonth, ReportingWeek, ReportingDay)
--)))|time_period
--|(((
++)))|(% style="width:221px" %)time_period
++|(% style="width:360px" %)(((
  ReportingYear
  (YYYY-A1 – 1 year period)
--)))|time_period
--|(((
++)))|(% style="width:221px" %)time_period
++|(% style="width:360px" %)(((
  ReportingSemester
  (YYYY-Ss – 6 month period)
--)))|time_period
--|(((
++)))|(% style="width:221px" %)time_period
++|(% style="width:360px" %)(((
  ReportingTrimester
  (YYYY-Tt – 4 month period)
--)))|time_period
--|(((
++)))|(% style="width:221px" %)time_period
++|(% style="width:360px" %)(((
  ReportingQuarter
  (YYYY-Qq – 3 month period)
--)))|time_period
--|(((
++)))|(% style="width:221px" %)time_period
++|(% style="width:360px" %)(((
  ReportingMonth
  (YYYY-Mmm – 1 month period)
--)))|time_period
--|ReportingWeek|time_period
--| (YYYY-Www – 7 day period; following ISO 8601 definition of a week in a year)|
--|(((
++)))|(% style="width:221px" %)time_period
++|(% style="width:360px" %)ReportingWeek|(% style="width:221px" %)time_period
++|(% style="width:360px" %) (YYYY-Www – 7 day period; following ISO 8601 definition of a week in a year)|(% style="width:221px" %)
++|(% style="width:360px" %)(((
  ReportingDay
  (YYYY-Dddd – 1 day period)
--)))|time_period
--|(((
++)))|(% style="width:221px" %)time_period
++|(% style="width:360px" %)(((
  DateTime
  (YYYY-MM-DDThh:mm:ss)
--)))|date
--|(((
++)))|(% style="width:221px" %)date
++|(% style="width:360px" %)(((
  TimeRange
--(YYYY-MM-DD(Thh:mm:ss)?/<duration>)
--)))|time
--|(((
++(YYYY-MM-DD(Thh:mm:ss)?/)
++)))|(% style="width:221px" %)time
++|(% style="width:360px" %)(((
  Month
--(~-~-MM; speicifies a month independent of a year; e.g. February is black history month in the United States)
--)))|string
--|(((
++(MM; speicifies a month independent of a year; e.g. February is black history month in the United States)
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
  MonthDay
--(~-~-MM-DD; specifies a day within a month independent of a year; e.g. Christmas is December 25^^th^^; used to specify reporting year start day)
--)))|string
--|(((
++(MM-DD; specifies a day within a month independent of a year; e.g. Christmas is December 25^^th^^; used to specify reporting year start day)
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
  Day
--(~-~--DD; specifies a day independent of a month or year; e.g. the 15^^th^^ is payday)
--)))|string
--|(((
++(-DD; specifies a day independent of a month or year; e.g. the 15^^th^^ is payday)
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
  Time
  (hh:mm:ss; time independent of a date; e.g. coffee break is at 10:00 AM)
--)))|string
--|(((
++)))|(% style="width:221px" %)string
++|(% style="width:360px" %)(((
  Duration
  (corresponds to XML Schema xs:duration datatype)
--)))|duration
--|XHTML|Metadata type – not applicable
--|KeyValues|Metadata type – not applicable
--|IdentifiableReference|Metadata type – not applicable
--|DataSetReference|Metadata type – not applicable
++)))|(% style="width:221px" %)duration
++|(% style="width:360px" %)XHTML|(% style="width:221px" %)Metadata type – not applicable
++|(% style="width:360px" %)KeyValues|(% style="width:221px" %)Metadata type – not applicable
++|(% style="width:360px" %)IdentifiableReference|(% style="width:221px" %)Metadata type – not applicable
++|(% style="width:360px" %)DataSetReference|(% style="width:221px" %)Metadata type – not applicable
  **Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types**
--When VTL takes in input SDMX artefacts, it is assumed that a type conversion according to the table above always happens. In case a different VTL basic scalar type is desired, it can be achieved in the VTL program taking in input the default VTL basic scalar type above and applying to it the VTL type conversion features (see the implicit and explicit type conversion and the "cast" operator in the VTL Reference Manual).
++When [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] takes in input [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]], it is assumed that a type conversion according to the table above always happens. In case a different [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar type is desired, it can be achieved in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] program taking in input the default [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar type above and applying to it the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] type conversion features (see the implicit and explicit type conversion and the "cast" operator in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Reference Manual).
  === 12.4.4 Mapping VTL basic scalar types to SDMX data types ===
  The following table describes the default conversion from the VTL basic scalar types to the SDMX data types .
--|(((
--VTL          basic
--scalar type
--)))|(((
++(% style="width:748.294px" %)
++|(% style="width:164px" %)(((
++VTL basic scalar type
++)))|(% style="width:304px" %)(((
  Default SDMX data type
--(BasicComponentDataType
--)
--)))|Default output format
--|String|String|Like XML (xs:string)
--|Number|Float|Like XML (xs:float)
--|Integer|Integer|Like XML (xs:int)
--|Date|DateTime|YYYY-MM-DDT00:00:00Z
--|Time|StandardTimePeriod|<date>/<date> (as defined above)
--|time_period|(((
++(BasicComponentDataType)
++)))|(% style="width:277px" %)Default output format
++|(% style="width:164px" %)String|(% style="width:304px" %)String|(% style="width:277px" %)Like XML (xs:string)
++|(% style="width:164px" %)Number|(% style="width:304px" %)Float|(% style="width:277px" %)Like XML (xs:float)
++|(% style="width:164px" %)Integer|(% style="width:304px" %)Integer|(% style="width:277px" %)Like XML (xs:int)
++|(% style="width:164px" %)Date|(% style="width:304px" %)DateTime|(% style="width:277px" %)YYYY-MM-DDT00:00:00Z
++|(% style="width:164px" %)Time|(% style="width:304px" %)StandardTimePeriod|(% style="width:277px" %)<date>/<date> (as defined above)
++|(% style="width:164px" %)time_period|(% style="width:304px" %)(((
  ReportingTimePeriod
  (StandardReportingPeriod)
--)))|(((
++)))|(% style="width:277px" %)(((
   YYYY-Pppp
  (according to SDMX )
  )))
--|Duration|Duration|Like     XML    (xs:duration) PnYnMnDTnHnMnS
--|Boolean|Boolean|Like XML (xs:boolean) with the values "true" or "false"
++|(% style="width:164px" %)Duration|(% style="width:304px" %)Duration|(% style="width:277px" %)Like XML (xs:duration) PnYnMnDTnHnMnS
++|(% style="width:164px" %)Boolean|(% style="width:304px" %)Boolean|(% style="width:277px" %)Like XML (xs:boolean) with the values "true" or "false"
  **Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types**
--In case a different default conversion is desired, it can be achieved through the CustomTypeScheme and CustomType artefacts (see also the section
++In case a different default conversion is desired, it can be achieved through the CustomTypeScheme and CustomType [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] (see also the section Transformations and Expressions of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] information model).
--Transformations and Expressions of the SDMX information model).
++The custom output formats can be specified by means of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] formatting mask described in the section "Type Conversion and Formatting Mask" of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Reference Manual. Such a section describes the masks for the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar types "number", "integer", "date", "time", "time_period" and "duration" and gives examples. As for the types "string" and "boolean" the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] conventions are extended with some other special characters as described in the following table.
--The custom output formats can be specified by means of the VTL formatting mask described in the section "Type Conversion and Formatting Mask" of the VTL Reference Manual. Such a section describes the masks for the VTL basic scalar types "number", "integer", "date", "time", "time_period" and "duration" and gives examples. As for the types "string" and "boolean" the VTL conventions are extended with some other special characters as described in the following table.
++(% style="width:717.294px" %)
++|(% colspan="2" style="width:714px" %)VTL special characters for the formatting masks
++|(% colspan="2" style="width:714px" %)
++|(% colspan="2" style="width:714px" %)Number
++|(% style="width:122px" %)D|(% style="width:591px" %)one numeric digit (if the scientific notation is adopted, D is only for the mantissa)
++|(% style="width:122px" %)E|(% style="width:591px" %)one numeric digit (for the exponent of the scientific notation)
++|(% style="width:122px" %). (dot)|(% style="width:591px" %)possible separator between the integer and the decimal parts.
++|(% style="width:122px" %), (comma)|(% style="width:591px" %)possible separator between the integer and the decimal parts.
++|(% style="width:122px" %) |(% style="width:591px" %)
++|(% colspan="2" style="width:714px" %)Time and duration
++|(% style="width:122px" %)C|(% style="width:591px" %)century
++|(% style="width:122px" %)Y|(% style="width:591px" %)year
++|(% style="width:122px" %)S|(% style="width:591px" %)semester
++|(% style="width:122px" %)Q|(% style="width:591px" %)quarter
++|(% style="width:122px" %)M|(% style="width:591px" %)month
++|(% style="width:122px" %)W|(% style="width:591px" %)week
++|(% style="width:122px" %)D|(% style="width:591px" %)day
++|(% style="width:122px" %)h|(% style="width:591px" %)hour digit (by default on 24 hours)
++|(% style="width:122px" %)M|(% style="width:591px" %)minute
++|(% style="width:122px" %)S|(% style="width:591px" %)second
++|(% style="width:122px" %)D|(% style="width:591px" %)decimal of second
++|(% style="width:122px" %)P|(% style="width:591px" %)period indicator (representation in one digit for the duration)
++|(% style="width:122px" %)P|(% style="width:591px" %)number of the periods specified in the period indicator
++|(% style="width:122px" %)AM/PM|(% style="width:591px" %)indicator of AM / PM (e.g. am/pm for "am" or "pm")
++|(% style="width:122px" %)MONTH|(% style="width:591px" %)uppercase textual representation of the month (e.g., JANUARY for January)
++|(% style="width:122px" %)DAY|(% style="width:591px" %)uppercase textual representation of the day (e.g., MONDAY for Monday)
++|(% style="width:122px" %)Month|(% style="width:591px" %)lowercase textual representation of the month (e.g., january)
++|(% style="width:122px" %)Day|(% style="width:591px" %)lowercase textual representation of the month (e.g., monday)
++|(% style="width:122px" %)Month|(% style="width:591px" %)First character uppercase, then lowercase textual representation of the month (e.g., January)
++|(% style="width:122px" %)Day|(% style="width:591px" %)First character uppercase, then lowercase textual representation of the day using (e.g. Monday)
++|(% style="width:122px" %) |(% style="width:591px" %)
++|(% colspan="2" style="width:714px" %)String
++|(% style="width:122px" %)X|(% style="width:591px" %)any string character
++|(% style="width:122px" %)Z|(% style="width:591px" %)any string character from "A" to "z"
++|(% style="width:122px" %)9|(% style="width:591px" %)any string character from "0" to "9"
++|(% style="width:122px" %) |(% style="width:591px" %)
++|(% colspan="2" style="width:714px" %)Boolean
++|(% style="width:122px" %)B|(% style="width:591px" %)Boolean using "true" for True and "false" for False
++|(% style="width:122px" %)1|(% style="width:591px" %)Boolean using "1" for True and "0" for False
++|(% style="width:122px" %)0|(% style="width:591px" %)Boolean using "0" for True and "1" for False
++|(% style="width:122px" %) |(% style="width:591px" %)
++|(% colspan="2" style="width:714px" %)Other qualifiers
++|(% style="width:122px" %)*|(% style="width:591px" %)an arbitrary number of digits (of the preceding type)
++|(% style="width:122px" %)+|(% style="width:591px" %)at least one digit (of the preceding type)
++|(% style="width:122px" %)( )|(% style="width:591px" %)optional digits (specified within the brackets)
++|(% style="width:122px" %)\|(% style="width:591px" %)prefix for the special characters that must appear in the mask
++|(% style="width:122px" %)N|(% style="width:591px" %)fixed number of digits used in the preceding textual representation of the month or the day
++|(% style="width:122px" %) |(% style="width:591px" %)
--|(% colspan="2" %)VTL special characters for the formatting masks
--|(% colspan="2" %)
--|(% colspan="2" %)Number
--|D|one numeric digit (if the scientific notation is adopted, D is only for the mantissa)
--|E|one numeric digit (for the exponent of the scientific notation)
--|. (dot)|possible separator between the integer and the decimal parts.
--|, (comma)|possible separator between the integer and the decimal parts.
--| |
--|(% colspan="2" %)Time and duration
--|C|century
--|Y|year
--|S|semester
--|Q|quarter
--|M|month
--|W|week
--|D|day
--|h|hour digit (by default on 24 hours)
--|M|minute
--|S|second
--|D|decimal of second
--|P|period indicator (representation in one digit for the duration)
--|P|number of the periods specified in the period indicator
--|AM/PM|indicator of AM / PM (e.g. am/pm for "am" or "pm")
--|MONTH|uppercase textual representation of the month (e.g., JANUARY for January)
--|DAY|uppercase textual representation of the day (e.g., MONDAY for Monday)
--|Month|lowercase textual representation of the month (e.g., january)
--|Day|lowercase textual representation of the month (e.g., monday)
--|Month|First character uppercase, then lowercase textual representation of the month (e.g., January)
--|Day|First character uppercase, then lowercase textual representation of the day using (e.g. Monday)
--| |
--|(% colspan="2" %)String
--|X|any string character
--|Z|any string character from "A" to "z"
--|9|any string character from "0" to "9"
--| |
--|(% colspan="2" %)Boolean
--|B|Boolean using "true" for True and "false" for False
--|1|Boolean using "1" for True and "0" for False
--|0|Boolean using "0" for True and "1" for False
--| |
--|(% colspan="2" %)Other qualifiers
--|*|an arbitrary number of digits (of the preceding type)
--|+|at least one digit (of the preceding type)
--|( )|optional digits (specified within the brackets)
--|\|prefix for the special characters that must appear in the mask
--|N|fixed number of digits used in the preceding textual representation of the month or the day
--| |
++The default conversion, either standard or customized, can be used to deduce automatically the [[representation>>doc:sdmx:Glossary.Representation.WebHome]] of the [[components>>doc:sdmx:Glossary.Component.WebHome]] of the result of a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformation. In alternative, the [[representation>>doc:sdmx:Glossary.Representation.WebHome]] of the resulting [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] can be given explicitly by providing its DataStructureDefinition. In other words, the [[representation>>doc:sdmx:Glossary.Representation.WebHome]] specified in the [[DSD>>doc:sdmx:Glossary.Data structure definition.WebHome]], if available, overrides any default conversion{{footnote}}The representation given in the DSD should obviously be compatible with the VTL data type.{{/footnote}}.
--The default conversion, either standard or customized, can be used to deduce automatically the representation of the components of the result of a VTL Transformation. In alternative, the representation of the resulting SDMX Dataflow can be given explicitly by providing its DataStructureDefinition. In other words, the representation specified in the DSD, if available, overrides any default conversion{{footnote}}The representation given in the DSD should obviously be compatible with the VTL data type.{{/footnote}}.
--
  === 12.4.3 Null Values ===
--In the conversions from SDMX to VTL it is assumed by default that a missing value in SDMX becomes a NULL in VTL. After the conversion, the NULLs can be manipulated through the proper VTL operators.
++In the conversions from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] it is assumed by default that a missing value in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] becomes a NULL in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]. After the conversion, the NULLs can be manipulated through the proper [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] operators.
--On the other side, the VTL programs can produce in output NULL values for Measures and Attributes (Null values are not allowed in the Identifiers). In the conversion from VTL to SDMX, it is assumed that a NULL in VTL becomes a missing value in SDMX. In the conversion from VTL to SDMX, the default assumption can be overridden, separately for each VTL basic scalar type, by specifying which the value that represents the NULL in SDMX is. This can be specified in the attribute "nullValue" of the CustomType artefact (see also the section Transformations and Expressions of the SDMX information model). A CustomType belongs to a CustomTypeScheme, which can be referenced by one or more TransformationScheme (i.e. VTL programs). The overriding assumption is applied for all the SDMX Dataflows calculated in the TransformationScheme.
++On the other side, the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] programs can produce in output NULL values for [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] and [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]] (Null values are not allowed in the Identifiers). In the conversion from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], it is assumed that a NULL in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] becomes a missing value in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]. In the conversion from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], the default assumption can be overridden, separately for each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar type, by specifying which the value that represents the NULL in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] is. This can be specified in the [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]] "nullValue" of the CustomType [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] (see also the section Transformations and Expressions of the [[SDMX information model>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]). A CustomType belongs to a CustomTypeScheme, which can be referenced by one or more TransformationScheme (i.e. [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] programs). The overriding assumption is applied for all the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]] calculated in the TransformationScheme.
  === 12.4.5 Format of the literals used in VTL Transformations ===
--The VTL programs can contain literals, i.e. specific values of certain data types written directly in the VTL definitions or expressions. The VTL does not prescribe a specific format for the literals and leave the specific VTL systems and the definers of VTL Transformations free of using their preferred formats.
++The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] programs can contain literals, i.e. specific values of certain data types written directly in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] definitions or expressions. The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] does not prescribe a specific format for the literals and leave the specific [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] systems and the definers of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Transformations free of using their preferred formats.
--Given this discretion, it is essential to know which are the external representations adopted for the literals in a VTL program, in order to interpret them correctly. For example, if the external format for the dates is YYYY-MM-DD the date literal 2010-0102 has the meaning of 2^^nd^^ January 2010, instead if the external format for the dates is YYYY-DD-MM the same literal has the meaning of 1^^st^^ February 2010.
++Given this discretion, it is essential to know which are the external [[representations>>doc:sdmx:Glossary.Representation.WebHome]] adopted for the literals in a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] program, in order to interpret them correctly. For example, if the external format for the dates is YYYY-MM-DD the date literal 2010-0102 has the meaning of 2^^nd^^ January 2010, instead if the external format for the dates is YYYY-DD-MM the same literal has the meaning of 1^^st^^ February 2010.
--Hereinafter, i.e. in the SDMX implementation of the VTL, it is assumed that the literals are expressed according to the "default output format" of the table of the previous paragraph ("Mapping VTL basic scalar types to SDMX data types") unless otherwise specified.
++Hereinafter, i.e. in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] implementation of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], it is assumed that the literals are expressed according to the "default output format" of the table of the previous paragraph ("Mapping [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar types to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data types") unless otherwise specified.
--A different format can be specified in the attribute "vtlLiteralFormat" of the CustomType artefact (see also the section Transformations and Expressions of the SDMX information model).
++A different format can be specified in the [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]] "vtlLiteralFormat" of the CustomType [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] (see also the section Transformations and Expressions of the [[SDMX information model>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]).
--Like in the case of the conversion of NULLs described in the previous paragraph, the overriding assumption is applied, for a certain VTL basic scalar type, if a value is found for the vtlLiteralFormat attribute of the CustomType of such VTL basic scalar type. The overriding assumption is applied for all the literals of a related VTL TransformationScheme.
++Like in the case of the conversion of NULLs described in the previous paragraph, the overriding assumption is applied, for a certain [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar type, if a value is found for the vtlLiteralFormat [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]] of the CustomType of such [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar type. The overriding assumption is applied for all the literals of a related [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] TransformationScheme.
--In case a literal is operand of a VTL Cast operation, the format specified in the Cast overrides all the possible otherwise specified formats.
++In case a literal is operand of a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Cast operation, the format specified in the Cast overrides all the possible otherwise specified formats.
  ----

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