Wiki source code of 12 Validation and Transformation Language (VTL)

Version 5.3 by Helena on 2025/06/16 14:08

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1.1	1	{{box title="Contents"}}
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1.11	5	== 12.1 Introduction ==
1.1	6
5.2	7	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:
1.1	8
	9	* definition of validation and transformation algorithms, in order to specify how to calculate new data from existing ones;
5.2	10	* 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);
	11	* 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.
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5.2	13	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").
1.1	14
5.2	15	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).
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5.2	17	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.
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5.2	19	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]].
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3.2	21	== 12.2 References to SDMX artefacts from VTL statements ==
1.15	22
1.11	23	=== 12.2.1 Introduction ===
1.1	24
5.2	25	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).
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5.2	27	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.
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5.2	29	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.
1.1	30
5.2	31	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.
1.1	32
	33	The references through the URN and the abbreviated URN are described in the following paragraphs.
	34
1.11	35	=== 12.2.2 References through the URN ===
1.1	36
5.2	37	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.
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5.2	39	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:
1.1	40
	41	* SDMXprefix
5.2	42	* [[SDMX-IM>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]-package-name
1.1	43	* class-name
	44	* agency-id
	45	* maintainedobject-id
5.2	46	* maintainedobject-(% style="color:#e74c3c" %)version
1.10	47	* container-object-id{{footnote}}The container-object-id can repeat and may not be present.{{/footnote}}
1.1	48	* object-id
	49
	50	The generic structure of the URN is the following:
	51
5.2	52	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
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5.2	54	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]].
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5.2	56	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".
1.1	57
5.2	58	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.
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5.2	60	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).
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5.2	62	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]]:
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5.2	64	* 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);
	65	* 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
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5.2	67	DataStructure maintainable class, the maintainedobject-id is the name of the DataStructure (dataStructure-id) which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] belongs to;
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5.2	69	* 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;
	70	* 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).
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5.2	72	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).
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5.2	74	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.
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5.2	76	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:
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5.2	78	* 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)
	79	* 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(%%))
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5.2	81	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
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5.2	83	{{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}}:
	84
1.18	85	> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' <-
	86	> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
	87	> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
1.1	88
1.11	89	=== 12.2.3 Abbreviation of the URN ===
1.1	90
5.2	91	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.
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5.2	93	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.
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5.2	95	* 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.
	96	* 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:
	97	** "datastructure" for the classes [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], TimeDimension, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]], DataAttribute,
	98	** "conceptscheme" for the class (% style="color:#e74c3c" %)Concept(%%),
1.16	99	** "codelist" for the class Codelist.
5.2	100	* 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}}.
	101	* 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).
1.17	102	* As for the maintainedobject-id, this is essential in some cases while in other cases it can be omitted:
5.2	103	** 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;
	104	** 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;
	105	** 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;
	106	** 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.
	107	* 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.
	108	* 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
	109	* 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]]
1.1	110
	111	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.
	112
	113	For example, the full formulation that uses the complete URN shown at the end of the previous paragraph:
	114
1.18	115	> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' :=
	116	> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
	117	> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
1.1	118
	119	by omitting all the non-essential parts would become simply:
	120
4.1	121	> DFR : = DF1 + DF2
1.1	122
1.9	123	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}}:
1.1	124
1.18	125	> 'urn:sdmx:org.sdmx.infomodel.codelist.Codelist=AG:CL_FREQ(1.0.0)'
1.1	126
	127	if the Codelist is referenced from a RulesetScheme belonging to the agency AG, omitting all the optional parts, the abbreviated reference would become simply^^19^^:
	128
1.18	129	> CL_FREQ
1.1	130
5.2	131	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:
1.1	132
1.18	133	> 'urn:sdmx:org.sdmx.infomodel.datastructure.DataStructure=AG:DST1(1.0.0).S ECTOR'
1.1	134
	135	The corresponding fully abbreviated reference, if made from a TransformationScheme belonging to AG, would become simply:
	136
1.18	137	> SECTOR
1.1	138
5.2	139	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}}:
1.1	140
1.18	141	> 'DFR(1.0.0)' := 'DF1(1.0.0)' [rename SECTOR to SEC]
1.1	142
5.2	143	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.
1.1	144
5.2	145	An example of non-abbreviated reference, if the conceptScheme-id is CS1 and the (% style="color:#e74c3c" %)concept(%%)-id is SECTOR, is the following:
1.1	146
1.18	147	> 'urn:sdmx:org.sdmx.infomodel.conceptscheme.Concept=AG:CS1(1.0.0).SECTOR'
1.1	148
	149	The corresponding fully abbreviated reference, if made from a RulesetScheme belonging to AG, would become simply:
	150
1.18	151	> CS1(1.0.0).SECTOR
1.1	152
5.2	153	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:
1.1	154
1.18	155	> 'DFR(1.0.0)' := between ( 'DF1(1.0.0)', 0, 25000 )
1.1	156
5.2	157	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).
1.1	158
1.11	159	=== 12.2.4 User-defined alias ===
1.1	160
5.2	161	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]].
1.1	162
5.2	163	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).
1.1	164
1.11	165	=== 12.2.5 References to SDMX artefacts from VTL Rulesets ===
1.1	166
5.2	167	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.
1.1	168
5.2	169	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.
1.1	170
5.2	171	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}}.
1.1	172
5.2	173	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}}
1.1	174
5.2	175	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.
1.1	176
1.11	177	== 12.3 Mapping between SDMX and VTL artefacts ==
1.15	178
1.11	179	=== 12.3.1. When the mapping occurs ===
1.1	180
5.2	181	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.
1.1	182
5.2	183	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}}.
1.1	184
5.2	185	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).
1.1	186
1.11	187	=== 12.3.2 General mapping of VTL and SDMX data structures ===
1.1	188
5.2	189	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}}.
1.1	190
5.2	191	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}}
1.1	192
5.2	193	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]].
1.1	194
5.2	195	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]].
1.1	196
5.2	197	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.
1.1	198
5.2	199	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.
1.1	200
	201	The possible mapping options are described in more detail in the following sections.
	202
1.20	203	=== 12.3.3 Mapping from SDMX to VTL data structures ===
1.1	204
1.11	205	==== 12.3.3.1 Basic Mapping ====
1.1	206
5.2	207	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.
1.1	208
5.2	209	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:
1.1	210
1.19	211	(% style="width:468.294px" %)
5.2	212	\|(% 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]]
	213	\|(% style="width:196px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]\|(% style="width:269px" %)(Simple) Identifier
1.19	214	\|(% style="width:196px" %)TimeDimension\|(% style="width:269px" %)(Time) Identifier
5.2	215	\|(% style="width:196px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]\|(% style="width:269px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]
	216	\|(% style="width:196px" %)DataAttribute\|(% style="width:269px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]
1.1	217
5.2	218	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]]).
1.1	219
5.2	220	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.
1.1	221
1.12	222	==== 12.3.3.2 Pivot Mapping ====
1.1	223
5.2	224	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]].
1.1	225
5.2	226	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}}.
1.1	227
5.2	228	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.
1.1	229
5.2	230	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).
1.1	231
5.2	232	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):
1.1	233
5.2	234	* 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;
	235	* 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]];
	236	* 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);
	237	* 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);
	238	* An [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute is (% style="color:#e74c3c" %)mapped(%%) in different ways according to its AttributeRelationship:
	239	** 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;
	240	** 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).
	241	** 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.
1.1	242
5.2	243	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:
1.1	244
1.21	245	(% style="width:739.294px" %)
5.2	246	\|(% 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]]
	247	\|(% style="width:335px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]\|(% style="width:400px" %)(Simple) Identifier
1.21	248	\|(% style="width:335px" %)TimeDimension\|(% style="width:400px" %)(Time) Identifier
5.2	249	\|(% 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
	250	\|(% style="width:335px" %)DataAttribute not depending on the MeasureDimension\|(% style="width:400px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]
1.21	251	\|(% style="width:335px" %)DataAttribute depending on the MeasureDimension\|(% style="width:400px" %)(((
5.2	252	One [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] for each [[Code>>doc:sdmx:Glossary.Code.WebHome]] of the
	253	[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension
1.1	254	)))
	255
5.2	256	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.
1.1	257
5.2	258	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:
1.1	259
5.2	260	* 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;
	261	* 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]].
	262	* 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
	263	* 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
1.1	264
1.12	265	==== 12.3.3.3 From SDMX DataAttributes to VTL Measures ====
1.1	266
5.2	267	* 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]].
1.1	268
5.2	269	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]].
1.1	270
5.2	271	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]].
1.1	272
1.12	273	=== 12.3.4 Mapping from VTL to SDMX data structures ===
1.1	274
1.12	275	==== 12.3.4.1 Basic Mapping ====
1.1	276
5.2	277	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.
1.1	278
	279	This is considered as the default mapping method and is applied unless a different method is specified through the VtlMappingScheme and VtlDataflowMapping classes.
	280
5.2	281	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.
1.1	282
	283	Mapping table:
	284
1.23	285	(% style="width:470.294px" %)
5.2	286	\|(% 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]]
	287	\|(% style="width:262px" %)(Simple) Identifier\|(% style="width:205px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]
1.23	288	\|(% style="width:262px" %)(Time) Identifier\|(% style="width:205px" %)TimeDimension
5.2	289	\|(% style="width:262px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]\|(% style="width:205px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]
	290	\|(% style="width:262px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]\|(% style="width:205px" %)DataAttribute
1.1	291
5.2	292	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.
1.1	293
5.2	294	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.
1.1	295
5.2	296	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.
1.1	297
5.2	298	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]].
1.1	299
1.12	300	==== 12.3.4.2 Unpivot Mapping ====
1.1	301
5.2	302	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.
1.1	303
5.2	304	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”.
1.1	305
5.2	306	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]].
1.1	307
	308	The unpivot mapping behaves like follows:
	309
5.2	310	* 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);
	311	* 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;
	312	* 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;
	313	* 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);
	314	* 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.
1.1	315
	316	The summary mapping table of the unpivot mapping method is the following:
	317
1.24	318	(% style="width:638.294px" %)
5.2	319	\|(% 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]]
	320	\|(% style="width:200px" %)(Simple) Identifier\|(% style="width:435px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]
1.24	321	\|(% style="width:200px" %)(Time) Identifier\|(% style="width:435px" %)TimeDimension
5.2	322	\|(% 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]]
	323	\|(% 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
1.1	324
5.2	325	At observation / data point (% style="color:#e74c3c" %)level(%%):
1.1	326
5.2	327	* 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]];
	328	* 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;
	329	* 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;
	330	* 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;
	331	* 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).
1.1	332
5.2	333	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”.
1.1	334
5.2	335	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]].
1.1	336
1.12	337	==== 12.3.4.3 From VTL Measures to SDMX Data Attributes ====
1.1	338
5.2	339	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”).
1.1	340
5.2	341	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.
1.1	342
	343	The mapping table is the following:
	344
1.24	345	(% style="width:467.294px" %)
5.2	346	\|(% 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]]
	347	\|(% style="width:214px" %)(Simple) Identifier\|(% style="width:250px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]
1.24	348	\|(% style="width:214px" %)(Time) Identifier\|(% style="width:250px" %)TimeDimension
5.2	349	\|(% style="width:214px" %)Some [[Measures>>doc:sdmx:Glossary.Measure.WebHome]]\|(% style="width:250px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]
	350	\|(% style="width:214px" %)Other [[Measures>>doc:sdmx:Glossary.Measure.WebHome]]\|(% style="width:250px" %)DataAttribute
	351	\|(% style="width:214px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]\|(% style="width:250px" %)DataAttribute
1.1	352
5.2	353	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]].
1.1	354
1.12	355	=== 12.3.5 Declaration of the mapping methods between data structures ===
1.1	356
5.2	357	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.
1.1	358
5.2	359	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.
1.1	360
5.2	361	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]].
1.1	362
5.2	363	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]]).
1.1	364
1.12	365	=== 12.3.6 Mapping dataflow subsets to distinct VTL Data Sets ===
1.1	366
5.2	367	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]]).
1.1	368
5.2	369	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}}
1.1	370
5.2	371	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}}
1.1	372
5.2	373	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]].
1.1	374
5.2	375	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:
1.1	376
5.2	377	* 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.
	378	* 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:
	379	** 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);
1.5	380	** 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}}
5.2	381	** 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
1.1	382
5.2	383	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.
1.1	384
5.2	385	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.
1.1	386
5.2	387	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:
1.1	388
1.24	389	> 'DF(1.0.0)/INDICATORvalue.COUNTRYvalue'
1.1	390
5.2	391	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:
1.1	392
1.24	393	> ‘DF(1.0.0)/POPULATION.USA’
1.1	394
5.2	395	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.
1.1	396
5.2	397	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]].
1.1	398
5.2	399	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.
1.1	400
5.2	401	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.
1.1	402
5.2	403	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
1.1	404
5.2	405	[[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.
1.1	406
5.2	407	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 …).
1.1	408
5.2	409	In the example above, for all the [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] of the kind
1.1	410
1.24	411	> ‘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.
1.1	412
5.2	413	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:
1.1	414
1.25	415	> ‘DF1(1.0.0)/POPULATION.USA’ :=
	416	> DF1(1.0.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“USA” ];
	417	>
	418	> ‘DF1(1.0.0)/POPULATION.CANADA’ :=
	419	> DF1(1.0.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“CANADA” ];
	420	>
	421	> … … …
1.1	422
5.2	423	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}}
1.1	424
5.2	425	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.
1.1	426
5.2	427	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.
1.1	428
5.2	429	This is equivalent to the application of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] “sub” operator only to the identifier //INDICATOR//:
1.1	430
1.25	431	> ‘DF1(1.0.0)/POPULATION.’ :=
	432	> DF1(1.0.0) [ sub INDICATOR=“POPULATION” ];
1.1	433
5.2	434	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.
1.1	435
5.2	436	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.
1.1	437
5.2	438	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]].
1.1	439
5.2	440	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.
1.1	441
5.2	442	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:
1.1	443
5.2	444	* 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}}
	445	* 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}}
1.1	446
5.2	447	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}}.
1.1	448
5.2	449	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
1.1	450
5.2	451	:{{footnote}}the symbol of the VTL persistent assignment is used (<-){{/footnote}}
	452
1.25	453	> ‘DF2(1.0.0)/INDICATORvalue.COUNTRYvalue’ <- expression
1.1	454
	455	Some examples follow, for some specific values of INDICATOR and COUNTRY:
	456
1.25	457	> ‘DF2(1.0.0)/GDPPERCAPITA.USA’ <- expression11; ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ <- expression12;
	458	> … … …
3.3	459	> ‘DF2(1.0.0)/POPGROWTH.USA’ <- expression21;
1.25	460	> ‘DF2(1.0.0)/POPGROWTH.CANADA’ <- expression22;
	461	> … … …
1.1	462
5.2	463	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:
1.1	464
4.1	465	> VTL dataset INDICATOR value COUNTRY value
3.3	466	>
4.1	467	> ‘DF2(1.0.0)/GDPPERCAPITA.USA’ GDPPERCAPITA USA
1.25	468	> ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ GDPPERCAPITA CANADA … … …
3.3	469	>
4.1	470	> ‘DF2(1.0.0)/POPGROWTH.USA’ POPGROWTH USA
	471	> ‘DF2(1.0.0)/POPGROWTH.CANADA’ POPGROWTH CANADA
1.25	472	> … … …
1.1	473
5.2	474	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:
1.1	475
4.1	476	> 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’,
1.25	477	> … ,
3.4	478	> DF2bis_POPGROWTH_USA’, DF2bis_POPGROWTH_CANADA’
1.25	479	> …);
1.1	480
5.2	481	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.
1.1	482
5.2	483	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}}
1.1	484
5.2	485	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).
1.1	486
1.13	487	=== 12.3.7 Mapping variables and value domains between VTL and SDMX ===
1.1	488
5.2	489	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:
1.1	490
1.25	491	(% style="width:706.294px" %)
5.2	492	\|(% 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]]
	493	\|(% 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^^
	494	\|(% style="width:257px" %)Represented Variable\|(% style="width:446px" %)(% style="color:#e74c3c" %)Concept(%%) with a definite [[Representation>>doc:sdmx:Glossary.Representation.WebHome]]
1.25	495	\|(% style="width:257px" %)Value Domain\|(% style="width:446px" %)(((
5.2	496	[[Representation>>doc:sdmx:Glossary.Representation.WebHome]] (see the Structure
1.1	497	Pattern in the Base Package)
	498	)))
5.2	499	\|(% style="width:257px" %)Enumerated Value Domain / [[Code List>>doc:sdmx:Glossary.Code list.WebHome]]\|(% style="width:446px" %)Codelist
	500	\|(% 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)
1.25	501	\|(% style="width:257px" %)Described Value Domain\|(% style="width:446px" %)(((
5.2	502	non-enumerated [[Representation>>doc:sdmx:Glossary.Representation.WebHome]]
	503	(having [[Facets>>doc:sdmx:Glossary.Facet.WebHome]] / ExtendedFacets, see the Structure Pattern in the Base Package)
1.1	504	)))
5.2	505	\|(% 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
	506	\|(% style="width:257px" %) \|(% style="width:446px" %)to a valid value (for non-enumerated [[Representations>>doc:sdmx:Glossary.Representation.WebHome]])
	507	\|(% 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]]
	508	\|(% 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]]
	509	\|(% 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]]
	510	\|(% style="width:257px" %)Set list\|(% style="width:446px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]
1.1	511
5.2	512	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).
1.1	513
5.2	514	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.
1.1	515
5.2	516	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
1.1	517
1.25	518	> DS_c := DS_a + DS_b (where DS_a, DS_b, DS_c are VTL Data Sets)
1.1	519
5.2	520	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.
1.25	521
5.2	522	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]]
1.1	523
5.2	524	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(%%).
1.1	525
5.2	526	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.
1.1	527
1.13	528	== 12.4 Mapping between SDMX and VTL Data Types ==
1.15	529
1.13	530	=== 12.4.1 VTL Data types ===
1.1	531
5.2	532	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.
1.1	533
5.2	534	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:
1.1	535
1.25	536	[[image:1750070288958-132.png]]
	537
1.13	538	Figure 22 – VTL Data Types
1.1	539
5.3	540	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.
1.1	541
5.3	542	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):
1.1	543
1.26	544	[[image:1750070310572-584.png]]
	545
1.13	546	Figure 23 – VTL Basic Scalar Types
1.1	547
1.13	548	=== 12.4.2 VTL basic scalar types and SDMX data types ===
1.1	549
5.3	550	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]].
1.1	551
5.3	552	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).
1.1	553
5.3	554	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).
1.1	555
5.3	556	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.
1.1	557
5.3	558	[[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).
1.1	559
5.3	560	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.
1.1	561
5.3	562	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.
1.1	563
5.3	564	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]].
1.1	565
1.13	566	=== 12.4.3 Mapping SDMX data types to VTL basic scalar types ===
1.1	567
5.3	568	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.
1.1	569
1.26	570	(% style="width:583.294px" %)
5.3	571	\|(% 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
1.26	572	\|(% style="width:360px" %)(((
1.1	573	String
	574	(string allowing any character)
1.26	575	)))\|(% style="width:221px" %)string
	576	\|(% style="width:360px" %)(((
	577	Alpha
1.1	578	(string which only allows A-z)
1.26	579	)))\|(% style="width:221px" %)string
	580	\|(% style="width:360px" %)(((
1.1	581	AlphaNumeric
	582	(string which only allows A-z and 0-9)
1.26	583	)))\|(% style="width:221px" %)string
	584	\|(% style="width:360px" %)(((
1.1	585	Numeric
	586	(string which only allows 0-9, but is not numeric so that is can having leading zeros)
1.26	587	)))\|(% style="width:221px" %)string
	588	\|(% style="width:360px" %)(((
1.1	589	BigInteger
	590	(corresponds to XML Schema xs:integer datatype; infinite set of integer values)
1.26	591	)))\|(% style="width:221px" %)integer
	592	\|(% style="width:360px" %)(((
1.1	593	Integer
	594	(corresponds to XML Schema xs:int datatype; between -2147483648 and +2147483647
	595	(inclusive))
1.26	596	)))\|(% style="width:221px" %)integer
	597	\|(% style="width:360px" %)(((
1.1	598	Long
	599	(corresponds to XML Schema xs:long datatype; between -9223372036854775808 and
	600	+9223372036854775807 (inclusive))
1.26	601	)))\|(% style="width:221px" %)integer
	602	\|(% style="width:360px" %)(((
1.1	603	Short
	604	(corresponds to XML Schema xs:short datatype; between -32768 and -32767 (inclusive))
1.26	605	)))\|(% style="width:221px" %)integer
5.3	606	\|(% 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
1.26	607	\|(% style="width:360px" %)(((
1.1	608	Float
	609	(corresponds to XML Schema xs:float datatype; patterned after the IEEE single-precision 32-bit floating point type)
1.26	610	)))\|(% style="width:221px" %)number
	611	\|(% style="width:360px" %)(((
1.1	612	Double
	613	(corresponds to XML Schema xs:double datatype; patterned after the IEEE double-precision 64-bit floating point type)
1.26	614	)))\|(% style="width:221px" %)number
	615	\|(% style="width:360px" %)(((
1.1	616	Boolean
5.3	617	(corresponds to the XML Schema xs:boolean datatype; support the mathematical (% style="color:#e74c3c" %)concept(%%) of
1.1	618	binary-valued logic: {true, false})
1.26	619	)))\|(% style="width:221px" %)boolean
	620	\|(% style="width:360px" %)(((
1.1	621	URI
	622	(corresponds to the XML Schema xs:anyURI; absolute or relative Uniform Resource Identifier Reference)
1.26	623	)))\|(% style="width:221px" %)string
	624	\|(% style="width:360px" %)(((
1.1	625	Count
	626	(an integer following a sequential pattern, increasing by 1 for each occurrence)
1.26	627	)))\|(% style="width:221px" %)integer
	628	\|(% style="width:360px" %)(((
1.1	629	InclusiveValueRange
5.3	630	([[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)
1.26	631	)))\|(% style="width:221px" %)number
	632	\|(% style="width:360px" %)(((
1.1	633	ExclusiveValueRange
5.3	634	([[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)
1.26	635	)))\|(% style="width:221px" %)number
	636	\|(% style="width:360px" %)(((
1.1	637	Incremental
5.3	638	([[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)
1.26	639	)))\|(% style="width:221px" %)number
	640	\|(% style="width:360px" %)(((
1.1	641	ObservationalTimePeriod
	642	(superset of StandardTimePeriod and TimeRange)
1.26	643	)))\|(% style="width:221px" %)time
	644	\|(% style="width:360px" %)(((
1.1	645	StandardTimePeriod
	646	(superset of BasicTimePeriod and ReportingTimePeriod)
1.26	647	)))\|(% style="width:221px" %)time
	648	\|(% style="width:360px" %)(((
1.1	649	BasicTimePeriod
	650	(superset of GregorianTimePeriod and DateTime)
1.26	651	)))\|(% style="width:221px" %)date
	652	\|(% style="width:360px" %)(((
1.1	653	GregorianTimePeriod
	654	(superset of GregorianYear, GregorianYearMonth, and GregorianDay)
1.26	655	)))\|(% style="width:221px" %)date
4.1	656	\|(% style="width:360px" %)GregorianYear (YYYY)\|(% style="width:221px" %)date
1.26	657	\|(% style="width:360px" %)GregorianYearMonth / GregorianMonth (YYYY-MM)\|(% style="width:221px" %)date
	658	\|(% style="width:360px" %)GregorianDay (YYYY-MM-DD)\|(% style="width:221px" %)date
	659	\|(% style="width:360px" %)(((
1.1	660	ReportingTimePeriod
	661	(superset of RepostingYear, ReportingSemester, ReportingTrimester, ReportingQuarter, ReportingMonth, ReportingWeek, ReportingDay)
1.26	662	)))\|(% style="width:221px" %)time_period
	663	\|(% style="width:360px" %)(((
1.1	664	ReportingYear
	665	(YYYY-A1 – 1 year period)
1.26	666	)))\|(% style="width:221px" %)time_period
	667	\|(% style="width:360px" %)(((
1.1	668	ReportingSemester
	669	(YYYY-Ss – 6 month period)
1.26	670	)))\|(% style="width:221px" %)time_period
	671	\|(% style="width:360px" %)(((
1.1	672	ReportingTrimester
	673	(YYYY-Tt – 4 month period)
1.26	674	)))\|(% style="width:221px" %)time_period
	675	\|(% style="width:360px" %)(((
1.1	676	ReportingQuarter
	677	(YYYY-Qq – 3 month period)
1.26	678	)))\|(% style="width:221px" %)time_period
	679	\|(% style="width:360px" %)(((
1.1	680	ReportingMonth
	681	(YYYY-Mmm – 1 month period)
1.26	682	)))\|(% style="width:221px" %)time_period
	683	\|(% style="width:360px" %)ReportingWeek\|(% style="width:221px" %)time_period
	684	\|(% style="width:360px" %) (YYYY-Www – 7 day period; following ISO 8601 definition of a week in a year)\|(% style="width:221px" %)
	685	\|(% style="width:360px" %)(((
1.1	686	ReportingDay
	687	(YYYY-Dddd – 1 day period)
1.26	688	)))\|(% style="width:221px" %)time_period
	689	\|(% style="width:360px" %)(((
1.1	690	DateTime
	691	(YYYY-MM-DDThh:mm:ss)
1.26	692	)))\|(% style="width:221px" %)date
	693	\|(% style="width:360px" %)(((
1.1	694	TimeRange
5.3	695	(YYYY-MM-DD(Thh:mm:ss)?/)
1.26	696	)))\|(% style="width:221px" %)time
	697	\|(% style="width:360px" %)(((
1.1	698	Month
5.3	699	(MM; speicifies a month independent of a year; e.g. February is black history month in the United States)
1.26	700	)))\|(% style="width:221px" %)string
	701	\|(% style="width:360px" %)(((
1.1	702	MonthDay
5.3	703	(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)
1.26	704	)))\|(% style="width:221px" %)string
	705	\|(% style="width:360px" %)(((
1.1	706	Day
5.3	707	(-DD; specifies a day independent of a month or year; e.g. the 15^^th^^ is payday)
1.26	708	)))\|(% style="width:221px" %)string
	709	\|(% style="width:360px" %)(((
1.1	710	Time
	711	(hh:mm:ss; time independent of a date; e.g. coffee break is at 10:00 AM)
1.26	712	)))\|(% style="width:221px" %)string
	713	\|(% style="width:360px" %)(((
1.1	714	Duration
	715	(corresponds to XML Schema xs:duration datatype)
1.26	716	)))\|(% style="width:221px" %)duration
	717	\|(% style="width:360px" %)XHTML\|(% style="width:221px" %)Metadata type – not applicable
	718	\|(% style="width:360px" %)KeyValues\|(% style="width:221px" %)Metadata type – not applicable
	719	\|(% style="width:360px" %)IdentifiableReference\|(% style="width:221px" %)Metadata type – not applicable
	720	\|(% style="width:360px" %)DataSetReference\|(% style="width:221px" %)Metadata type – not applicable
1.1	721
1.14	722	Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types
1.1	723
5.3	724	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).
1.1	725
1.14	726	=== 12.4.4 Mapping VTL basic scalar types to SDMX data types ===
1.1	727
	728	The following table describes the default conversion from the VTL basic scalar types to the SDMX data types .
	729
1.26	730	(% style="width:748.294px" %)
	731	\|(% style="width:164px" %)(((
	732	VTL basic scalar type
	733	)))\|(% style="width:304px" %)(((
1.1	734	Default SDMX data type
1.26	735	(BasicComponentDataType)
	736	)))\|(% style="width:277px" %)Default output format
	737	\|(% style="width:164px" %)String\|(% style="width:304px" %)String\|(% style="width:277px" %)Like XML (xs:string)
	738	\|(% style="width:164px" %)Number\|(% style="width:304px" %)Float\|(% style="width:277px" %)Like XML (xs:float)
	739	\|(% style="width:164px" %)Integer\|(% style="width:304px" %)Integer\|(% style="width:277px" %)Like XML (xs:int)
	740	\|(% style="width:164px" %)Date\|(% style="width:304px" %)DateTime\|(% style="width:277px" %)YYYY-MM-DDT00:00:00Z
	741	\|(% style="width:164px" %)Time\|(% style="width:304px" %)StandardTimePeriod\|(% style="width:277px" %)<date>/<date> (as defined above)
	742	\|(% style="width:164px" %)time_period\|(% style="width:304px" %)(((
1.1	743	ReportingTimePeriod
	744	(StandardReportingPeriod)
1.26	745	)))\|(% style="width:277px" %)(((
1.1	746	YYYY-Pppp
	747	(according to SDMX )
	748	)))
1.26	749	\|(% style="width:164px" %)Duration\|(% style="width:304px" %)Duration\|(% style="width:277px" %)Like XML (xs:duration) PnYnMnDTnHnMnS
	750	\|(% style="width:164px" %)Boolean\|(% style="width:304px" %)Boolean\|(% style="width:277px" %)Like XML (xs:boolean) with the values "true" or "false"
1.1	751
1.14	752	Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types
1.1	753
5.3	754	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).
1.1	755
5.3	756	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.
1.1	757
1.26	758	(% style="width:717.294px" %)
	759	\|(% colspan="2" style="width:714px" %)VTL special characters for the formatting masks
	760	\|(% colspan="2" style="width:714px" %)
	761	\|(% colspan="2" style="width:714px" %)Number
	762	\|(% style="width:122px" %)D\|(% style="width:591px" %)one numeric digit (if the scientific notation is adopted, D is only for the mantissa)
	763	\|(% style="width:122px" %)E\|(% style="width:591px" %)one numeric digit (for the exponent of the scientific notation)
	764	\|(% style="width:122px" %). (dot)\|(% style="width:591px" %)possible separator between the integer and the decimal parts.
	765	\|(% style="width:122px" %), (comma)\|(% style="width:591px" %)possible separator between the integer and the decimal parts.
	766	\|(% style="width:122px" %) \|(% style="width:591px" %)
	767	\|(% colspan="2" style="width:714px" %)Time and duration
	768	\|(% style="width:122px" %)C\|(% style="width:591px" %)century
	769	\|(% style="width:122px" %)Y\|(% style="width:591px" %)year
	770	\|(% style="width:122px" %)S\|(% style="width:591px" %)semester
	771	\|(% style="width:122px" %)Q\|(% style="width:591px" %)quarter
	772	\|(% style="width:122px" %)M\|(% style="width:591px" %)month
	773	\|(% style="width:122px" %)W\|(% style="width:591px" %)week
	774	\|(% style="width:122px" %)D\|(% style="width:591px" %)day
	775	\|(% style="width:122px" %)h\|(% style="width:591px" %)hour digit (by default on 24 hours)
	776	\|(% style="width:122px" %)M\|(% style="width:591px" %)minute
	777	\|(% style="width:122px" %)S\|(% style="width:591px" %)second
	778	\|(% style="width:122px" %)D\|(% style="width:591px" %)decimal of second
	779	\|(% style="width:122px" %)P\|(% style="width:591px" %)period indicator (representation in one digit for the duration)
	780	\|(% style="width:122px" %)P\|(% style="width:591px" %)number of the periods specified in the period indicator
	781	\|(% style="width:122px" %)AM/PM\|(% style="width:591px" %)indicator of AM / PM (e.g. am/pm for "am" or "pm")
	782	\|(% style="width:122px" %)MONTH\|(% style="width:591px" %)uppercase textual representation of the month (e.g., JANUARY for January)
	783	\|(% style="width:122px" %)DAY\|(% style="width:591px" %)uppercase textual representation of the day (e.g., MONDAY for Monday)
	784	\|(% style="width:122px" %)Month\|(% style="width:591px" %)lowercase textual representation of the month (e.g., january)
	785	\|(% style="width:122px" %)Day\|(% style="width:591px" %)lowercase textual representation of the month (e.g., monday)
	786	\|(% style="width:122px" %)Month\|(% style="width:591px" %)First character uppercase, then lowercase textual representation of the month (e.g., January)
	787	\|(% style="width:122px" %)Day\|(% style="width:591px" %)First character uppercase, then lowercase textual representation of the day using (e.g. Monday)
	788	\|(% style="width:122px" %) \|(% style="width:591px" %)
	789	\|(% colspan="2" style="width:714px" %)String
	790	\|(% style="width:122px" %)X\|(% style="width:591px" %)any string character
	791	\|(% style="width:122px" %)Z\|(% style="width:591px" %)any string character from "A" to "z"
	792	\|(% style="width:122px" %)9\|(% style="width:591px" %)any string character from "0" to "9"
	793	\|(% style="width:122px" %) \|(% style="width:591px" %)
	794	\|(% colspan="2" style="width:714px" %)Boolean
	795	\|(% style="width:122px" %)B\|(% style="width:591px" %)Boolean using "true" for True and "false" for False
	796	\|(% style="width:122px" %)1\|(% style="width:591px" %)Boolean using "1" for True and "0" for False
	797	\|(% style="width:122px" %)0\|(% style="width:591px" %)Boolean using "0" for True and "1" for False
	798	\|(% style="width:122px" %) \|(% style="width:591px" %)
	799	\|(% colspan="2" style="width:714px" %)Other qualifiers
	800	\|(% style="width:122px" %)*\|(% style="width:591px" %)an arbitrary number of digits (of the preceding type)
	801	\|(% style="width:122px" %)+\|(% style="width:591px" %)at least one digit (of the preceding type)
	802	\|(% style="width:122px" %)( )\|(% style="width:591px" %)optional digits (specified within the brackets)
	803	\|(% style="width:122px" %)\\|(% style="width:591px" %)prefix for the special characters that must appear in the mask
	804	\|(% style="width:122px" %)N\|(% style="width:591px" %)fixed number of digits used in the preceding textual representation of the month or the day
	805	\|(% style="width:122px" %) \|(% style="width:591px" %)
1.1	806
5.3	807	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}}.
1.1	808
1.14	809	=== 12.4.3 Null Values ===
1.1	810
5.3	811	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.
1.1	812
5.3	813	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.
1.1	814
1.14	815	=== 12.4.5 Format of the literals used in VTL Transformations ===
1.1	816
5.3	817	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.
1.1	818
5.3	819	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.
1.1	820
5.3	821	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.
1.1	822
5.3	823	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]]).
1.1	824
5.3	825	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.
1.1	826
5.3	827	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.
1.1	828
	829	----
	830
	831	{{putFootnotes/}}