Wiki source code of 10 Validation and Transformation Language (VTL)
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| 1 | = 10 Validation and Transformation Language (VTL) = | ||
| 2 | |||
| 3 | == 10.1 Introduction == | ||
| 4 | |||
| 5 | 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: | ||
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| 7 | * definition of validation and transformation algorithms, in order to specify how to calculate new data from existing ones; | ||
| 8 | * 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); | ||
| 9 | * 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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| 11 | 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”). | ||
| 12 | |||
| 13 | 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. 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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| 15 | 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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| 17 | 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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| 19 | == 10.2 References to SDMX artefacts from VTL statements == | ||
| 20 | |||
| 21 | === 10.2.1 Introduction === | ||
| 22 | |||
| 23 | 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 pre-defined conventional names (aliases). | ||
| 24 | |||
| 25 | The alias of a [[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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| 27 | 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 VTLMapping are used also for User Defined Operators (UDO). Although UDOperators 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 UDOperator 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. | ||
| 28 | |||
| 29 | 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. | ||
| 30 | |||
| 31 | The references through the URN and the abbreviated URN are described in the following paragraphs. | ||
| 32 | |||
| 33 | === 10.2.2 References through the URN === | ||
| 34 | |||
| 35 | This approach has the advantage that in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[code>>doc:sdmx:Glossary.Code.WebHome]] 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. | ||
| 36 | |||
| 37 | 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}} is the concatenation of the following parts, separated by special symbols like dot, equal, asterisk, comma, and parenthesis: | ||
| 38 | |||
| 39 | * SDMXprefix | ||
| 40 | * SDMX-IM-package-name | ||
| 41 | * class-name | ||
| 42 | * agency-id | ||
| 43 | * maintainedobject-id | ||
| 44 | * maintainedobject-version | ||
| 45 | * container-object-id{{footnote}}The container-object-id can repeat and may not be present.{{/footnote}} | ||
| 46 | * object-id | ||
| 47 | |||
| 48 | The generic structure of the URN is the following: | ||
| 49 | |||
| 50 | SDMXprefix**.**SDMX-IM-package-name**.**class-name**=**agency-id**:**maintainedobject-id **(**maintainedobject-version**).***container-object-id**.**object-id | ||
| 51 | |||
| 52 | The **[[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] prefix** is “urn:sdmx:org”, always the same for all [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]]. | ||
| 53 | |||
| 54 | 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-package-name is “sdmx.infomodel.datastructure”, because the class [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] belongs to the package “datastructure”. | ||
| 55 | |||
| 56 | 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]], MeasureDimension, TimeDimension, PrimaryMeasure, DataAttribute, (% style="color:#e74c3c" %)Concept(%%), ConceptScheme, Codelist. | ||
| 57 | |||
| 58 | 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). | ||
| 59 | |||
| 60 | 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]]: | ||
| 61 | |||
| 62 | * 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); | ||
| 63 | * if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], MeasureDimension, TimeDimension, PrimaryMeasure or DataAttribute, which are not maintainable and belong to the DataStructure maintainable class, the maintainedobject-id is the name of the DataStructure (dataStructure-id) which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] belongs to; | ||
| 64 | * 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; | ||
| 65 | * if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a ConceptScheme, which is a maintainable class, the maintainedobject-id is the name of the ConceptScheme (conceptScheme-id); | ||
| 66 | * 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). | ||
| 67 | |||
| 68 | The **maintainedobject-(% style="color:#e74c3c" %)version(%%)** is the (% style="color:#e74c3c" %)version(%%) of the maintained object which the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] belongs to (for example, possible (% style="color:#e74c3c" %)versions(%%) are 1.0, 2.1, 3.1.2). | ||
| 69 | |||
| 70 | 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 | ||
| 71 | |||
| 72 | 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: | ||
| 73 | |||
| 74 | * if the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], MeasureDimension, TimeDimension, PrimaryMeasure or DataAttribute (the object-id is the name of one of the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] above, which are data structure [[components>>doc:sdmx:Glossary.Component.WebHome]]) | ||
| 75 | * 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(%%)) | ||
| 76 | |||
| 77 | 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 and their Agency is AG, would be written as{{footnote}}Since these references to SDMX objects include non-permitted characters as per the VTL ID notation, they need to be included between single quotes, according to the VTL rules for irregular names.{{/footnote}}: | ||
| 78 | |||
| 79 | ‘urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0)’ <- | ||
| 80 | ‘urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0)’ + | ||
| 81 | ‘urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0)’ | ||
| 82 | |||
| 83 | === 10.2.3 Abbreviation of the URN === | ||
| 84 | |||
| 85 | 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. | ||
| 86 | |||
| 87 | 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. | ||
| 88 | |||
| 89 | * 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. | ||
| 90 | * 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: | ||
| 91 | ** “datastructure” for the classes [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], MeasureDimension, TimeDimension, PrimaryMeasure, DataAttribute, | ||
| 92 | ** “conceptscheme” for the classes (% style="color:#e74c3c" %)Concept(%%) and ConceptScheme | ||
| 93 | ** “codelist” for the class Codelist. | ||
| 94 | * 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, MeasureDimension, TimeDimension, PrimaryMeasure or DataAttribute) can be deduced from the data structure of the SDMX Dataflow which the component belongs to.{{/footnote}}. | ||
| 95 | * 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 agency-id 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}}(% style="font-size:12px" %) (%%)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). | ||
| 96 | * As for the **maintainedobject-id**, this is essential in some cases while in other cases it can be omitted: o 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; | ||
| 97 | ** if the referenced [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], MeasureDimension, TimeDimension, PrimaryMeasure, 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; | ||
| 98 | ** 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; | ||
| 99 | ** if the referenced [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] is a ConceptScheme, which is a,, ,,maintainable class,,, ,,the maintained object is the conceptScheme-id and obviously cannot be omitted; | ||
| 100 | ** 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. | ||
| 101 | * 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. | ||
| 102 | * 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 | ||
| 103 | * The **object-id** does not exist for the [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] belonging to the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]], ConceptScheme 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]], MeasureDimension, TimeDimension, PrimaryMeasure, DataAttribute and (% style="color:#e74c3c" %)Concept(%%), as for them the object-id is the main identifier of the [[artefact>>doc:sdmx:Glossary.Artefact.WebHome]] | ||
| 104 | |||
| 105 | 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. | ||
| 106 | |||
| 107 | For example, the full formulation that uses the complete URN shown at the end of the previous paragraph: | ||
| 108 | |||
| 109 | ‘urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0)’ := | ||
| 110 | ‘urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0)’ + | ||
| 111 | ‘urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0)’ | ||
| 112 | |||
| 113 | by omitting all the non-essential parts would become simply: | ||
| 114 | |||
| 115 | DFR := DF1 + DF2 | ||
| 116 | |||
| 117 | The references to the Codelists can be simplified similarly. For example, given the non-abbreviated reference to the Codelist AG:CL_FREQ(1.0), which is{{footnote}}Single quotes are needed because this reference is not a VTL regular name.{{/footnote}}: | ||
| 118 | |||
| 119 | ‘urn:sdmx:org.sdmx.infomodel.codelist.Codelist=AG:CL_FREQ(1.0)’ | ||
| 120 | |||
| 121 | if the Codelist is referenced from a ruleset scheme belonging to the agency AG, omitting all the optional parts, the abbreviated reference would become simply{{footnote}}Single quotes are not needed in this case because CL_FREQ is a VTL regular name.{{/footnote}}: | ||
| 122 | |||
| 123 | CL_FREQ | ||
| 124 | |||
| 125 | As for the references to the components, it can be enough to specify the componentId, given that the dataStructure-Id can be omitted. An example of non-abbreviated reference, if the data structure is DST1 and the component is SECTOR, is the following: | ||
| 126 | |||
| 127 | ‘urn:sdmx:org.sdmx.infomodel.datastructure.DataStructure=AG:DST1(1.0).SECTOR’ | ||
| 128 | |||
| 129 | The corresponding fully abbreviated reference, if made from a transformation scheme belonging to AG, would become simply: | ||
| 130 | |||
| 131 | SECTOR | ||
| 132 | |||
| 133 | 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) is be equal to DF1(1.0) save that the component SECTOR is called SEC{{/footnote}}: | ||
| 134 | |||
| 135 | ‘DFR(1.0)’ := ‘DF1(1.0)’ [rename SECTOR to SEC] | ||
| 136 | |||
| 137 | 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. | ||
| 138 | |||
| 139 | An example of non-abbreviated reference, if the conceptScheme-id is CS1 and the (% style="color:#e74c3c" %)concept(%%)-id is SECTOR, is the following: | ||
| 140 | |||
| 141 | ‘urn:sdmx:org.sdmx.infomodel.conceptscheme.(% style="color:#e74c3c" %)Concept(%%)=AG:CS1(1.0).SECTOR’ | ||
| 142 | |||
| 143 | The corresponding fully abbreviated reference, if made from a RulesetScheme belonging to AG, would become simply: | ||
| 144 | |||
| 145 | CS1(1.0).SECTOR | ||
| 146 | |||
| 147 | 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: | ||
| 148 | |||
| 149 | ‘DFR(1.0)’ := between ( ‘DF1(1.0)’, 0, 25000 ) | ||
| 150 | |||
| 151 | 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). | ||
| 152 | |||
| 153 | === 10.2.4 User-defined alias === | ||
| 154 | |||
| 155 | 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]]. | ||
| 156 | |||
| 157 | 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 the referenced [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] would 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). | ||
| 158 | |||
| 159 | === 10.2.5 References to SDMX artefacts from VTL Rulesets === | ||
| 160 | |||
| 161 | The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Rulesets allow defining sets of reusable rules that can be applied by some | ||
| 162 | |||
| 163 | [[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. | ||
| 164 | |||
| 165 | 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. | ||
| 166 | |||
| 167 | 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 or to a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] ConceptScheme (for [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]]), 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{{footnote}}Rulesets of this kind cannot be reused when the referenced Concept has a different representation.{{/footnote}}. | ||
| 168 | |||
| 169 | 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}} | ||
| 170 | |||
| 171 | 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, ConceptScheme, (% style="color:#e74c3c" %)Concept(%%)) to can be deduced from the Ruleset signature. | ||
| 172 | |||
| 173 | == 10.3 Mapping between SDMX and VTL artefacts == | ||
| 174 | |||
| 175 | === 10.3.1 When the mapping occurs === | ||
| 176 | |||
| 177 | 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. | ||
| 178 | |||
| 179 | 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.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]]. | ||
| 180 | |||
| 181 | 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. | ||
| 182 | |||
| 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. Also possible calculated artefact that are not persistent may require a SDMX definition, for example when the result of a non-persistent calculation is disseminated through SDMX tools (like an inquiry tool).{{/footnote}}. | ||
| 184 | |||
| 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 assignmentStatus 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). | ||
| 186 | |||
| 187 | === 10.3.2 General mapping of VTL and SDMX data structures === | ||
| 188 | |||
| 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>>doc:sdmx:Glossary.Data structure definition.WebHome]]”{{footnote}}See the SDMX 2.1 Section 2 – Information Model{{/footnote}} | ||
| 190 | |||
| 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}} | ||
| 192 | |||
| 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]]. | ||
| 194 | |||
| 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]]. | ||
| 196 | |||
| 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, PrimaryMeasure 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]], a TimeDimension or a MeasureDimension. 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 three sub-classes (Simple Identifier, Time Identifier, [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] Identifier) even if such a distinction is not evidenced in the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] IM. | ||
| 198 | |||
| 199 | However, a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] Data Structure can have any number of Identifiers, [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] and [[Attributes>>doc:sdmx:Glossary.Attribute.WebHome]], while a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 DataStructureDefinition can have any number of [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] and DataAttributes but just one PrimaryMeasure{{footnote}}The SDMX community is evaluating the opportunity of allowing more than one measure component in a DataStructureDefinition in the next SDMX major version.{{/footnote}}. This is due to a difference between [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 and [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] in the possible [[representation>>doc:sdmx:Glossary.Representation.WebHome]] methods of the data that contain more [[measures>>doc:sdmx:Glossary.Measure.WebHome]]. | ||
| 200 | |||
| 201 | As for [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], because the data structure cannot contain more than one [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]] (i.e., the primaryMeasure), the [[representation>>doc:sdmx:Glossary.Representation.WebHome]] of data having more [[measures>>doc:sdmx:Glossary.Measure.WebHome]] is possible only by means of a particular [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]], called MeasureDimension, which is aimed at containing the name of the [[measure>>doc:sdmx:Glossary.Measure.WebHome]] (% style="color:#e74c3c" %)concepts(%%), so that for each observation the value contained in the PrimaryMeasure [[component>>doc:sdmx:Glossary.Component.WebHome]] is the value of the [[measure>>doc:sdmx:Glossary.Measure.WebHome]] (% style="color:#e74c3c" %)concept(%%) reported in the MeasureDimension [[component>>doc:sdmx:Glossary.Component.WebHome]]. | ||
| 202 | |||
| 203 | Instead [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] allows either the method above (an identifier containing the name of the [[measure>>doc:sdmx:Glossary.Measure.WebHome]] together with just one [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]]) or a more generic method that consists in defining more [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[components>>doc:sdmx:Glossary.Component.WebHome]] in the data structure, one for each [[measure>>doc:sdmx:Glossary.Measure.WebHome]]. | ||
| 204 | |||
| 205 | Therefore for multi-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] data more mapping options are possible, as described in more detail in the following sections. | ||
| 206 | |||
| 207 | === 10.3.3 Mapping from SDMX to VTL data structures === | ||
| 208 | |||
| 209 | ==== 10.3.3.1 Basic Mapping** ** ==== | ||
| 210 | |||
| 211 | 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. | ||
| 212 | |||
| 213 | 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: | ||
| 214 | |||
| 215 | (% style="width:636.294px" %) | ||
| 216 | |(% style="width:286px" %)**SDMX**|(% style="width:347px" %)**VTL** | ||
| 217 | |(% style="width:286px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]|(% style="width:347px" %)(Simple) Identifier | ||
| 218 | |(% style="width:286px" %)Time [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]|(% style="width:347px" %)(Time) Identifier | ||
| 219 | |(% style="width:286px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]|(% style="width:347px" %)([[Measure>>doc:sdmx:Glossary.Measure.WebHome]]) Identifier | ||
| 220 | |(% style="width:286px" %)Primary [[Measure>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:347px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]] | ||
| 221 | |(% style="width:286px" %)Data [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]|(% style="width:347px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] | ||
| 222 | |||
| 223 | According to this method, the resulting [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures are always mono-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] (i.e., they have just one [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]]) and their [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] is the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] PrimaryMeasure. Nevertheless, if the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data structure has a MeasureDimension, which can convey the name of one or more [[measure>>doc:sdmx:Glossary.Measure.WebHome]] (% style="color:#e74c3c" %)concepts(%%), such unique [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]] can contain the value of more (conceptual) [[measures>>doc:sdmx:Glossary.Measure.WebHome]] (one for each observation). | ||
| 224 | |||
| 225 | As for 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]]). | ||
| 226 | |||
| 227 | With the Basic mapping, one [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] observation generates one [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data point. | ||
| 228 | |||
| 229 | ==== 10.3.3.2 Pivot Mapping ==== | ||
| 230 | |||
| 231 | 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 is different from the Basic method only for the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data structures that contain a MeasureDimension, which are (% style="color:#e74c3c" %)mapped(%%) to multi-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] data structures. | ||
| 232 | |||
| 233 | The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] structures that do not contain a MeasureDimension are (% style="color:#e74c3c" %)mapped(%%) like in the Basic mapping (see the previous paragraph). | ||
| 234 | |||
| 235 | The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] structures that contain a MeasureDimension are (% style="color:#e74c3c" %)mapped(%%) as follows (this mapping is equivalent to a pivoting operation): | ||
| 236 | |||
| 237 | * 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; | ||
| 238 | * Each possible (% style="color:#e74c3c" %)Concept(%%) 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]] (% style="color:#e74c3c" %)Concept(%%) (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]]; | ||
| 239 | * 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); | ||
| 240 | * The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] PrimaryMeasure 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); | ||
| 241 | * A [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute is (% style="color:#e74c3c" %)mapped(%%) in different ways according to its AttributeRelationship: | ||
| 242 | ** 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; | ||
| 243 | ** 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 (% style="color:#e74c3c" %)Concept(%%) 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 | ||
| 244 | |||
| 245 | (% style="color:#e74c3c" %)Concept(%%) 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 (% style="color:#e74c3c" %)concepts(%%) 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). o 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. | ||
| 246 | |||
| 247 | 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: | ||
| 248 | |||
| 249 | (% style="width:941.294px" %) | ||
| 250 | |(% style="width:441px" %)**SDMX**|(% style="width:497px" %)**VTL** | ||
| 251 | |(% style="width:441px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]]|(% style="width:497px" %)(Simple) Identifier | ||
| 252 | |(% style="width:441px" %)TimeDimension|(% style="width:497px" %)(Time) Identifier | ||
| 253 | |(% style="width:441px" %)MeasureDimension & PrimaryMeasure|(% style="width:497px" %)One [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] for each (% style="color:#e74c3c" %)Concept(%%) of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] | ||
| 254 | |(% style="width:441px" %)DataAttribute not depending on the MeasureDimension|(% style="width:497px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] | ||
| 255 | |(% style="width:441px" %)DataAttribute depending on the MeasureDimension|(% style="width:497px" %)One [[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] for each (% style="color:#e74c3c" %)Concept(%%) of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] | ||
| 256 | |||
| 257 | 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. | ||
| 258 | |||
| 259 | At observation / data point (% style="color:#e74c3c" %)level(%%), calling Cj (j=1, … n) the j^^th^^ (% style="color:#e74c3c" %)Concept(%%) of the MeasureDimension: | ||
| 260 | |||
| 261 | * 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 (% style="color:#e74c3c" %)Concept(%%) Cj of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension; | ||
| 262 | * 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]]. | ||
| 263 | * The value of the PrimaryMeasure 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 | ||
| 264 | * 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 | ||
| 265 | |||
| 266 | ==== 10.3.3.3 From SDMX DataAttributes to VTL Measures ==== | ||
| 267 | |||
| 268 | * 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]]. | ||
| 269 | |||
| 270 | 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]]. | ||
| 271 | |||
| 272 | 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]]. | ||
| 273 | |||
| 274 | === 10.3.4 Mapping from VTL to SDMX data structures === | ||
| 275 | |||
| 276 | ==== 10.3.4.1 Basic Mapping** ** ==== | ||
| 277 | |||
| 278 | 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. | ||
| 279 | |||
| 280 | This is considered as the default mapping method and is applied unless a different method is specified through the VtlMappingScheme and VtlDataflowMapping classes. | ||
| 281 | |||
| 282 | 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. | ||
| 283 | |||
| 284 | This mapping method cannot be applied for [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 if 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]], given that the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 DataStructureDefinition allows just one [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]] (the PrimaryMeasure). In this case it becomes mandatory to specify a different mapping method through the VtlMappingScheme and VtlDataflowMapping classes.{{footnote}}If future SDMX major versions will allow multi-measures data structures, this method is expected to become applicable even if the VTL data structure has more than one measure{{/footnote}} | ||
| 285 | |||
| 286 | Please note that the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[measures>>doc:sdmx:Glossary.Measure.WebHome]] can have any name while in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 the MeasureComponent has the mandatory name “obs_value”, therefore the name of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[measure>>doc:sdmx:Glossary.Measure.WebHome]] name must become “obs_value” in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1. | ||
| 287 | |||
| 288 | Mapping table: | ||
| 289 | |||
| 290 | (% style="width:592.294px" %) | ||
| 291 | |(% style="width:253px" %)**VTL**|(% style="width:336px" %)**SDMX** | ||
| 292 | |(% style="width:253px" %)(Simple) Identifier|(% style="width:336px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] | ||
| 293 | |(% style="width:253px" %)(Time) Identifier|(% style="width:336px" %)TimeDimension | ||
| 294 | |(% style="width:253px" %)([[Measure>>doc:sdmx:Glossary.Measure.WebHome]]) Identifier|(% style="width:336px" %)MeasureDimension | ||
| 295 | |(% style="width:253px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:336px" %)PrimaryMeasure | ||
| 296 | |(% style="width:253px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]|(% style="width:336px" %)DataAttribute | ||
| 297 | |||
| 298 | If the distinction between simple identifier, time identifier and [[measure>>doc:sdmx:Glossary.Measure.WebHome]] 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]], TimeDimension and MeasureDimension exists only in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]], as declared in the relevant DataStructureDefinition. | ||
| 299 | |||
| 300 | 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 (AttributeRelationships referred to the PrimaryMeasure), unless some other information about their AttributeRelationship is available. | ||
| 301 | |||
| 302 | Note that the basic mappings in the two directions (from [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] 2.0 and vice-versa) are (almost completely) reversible. In fact, if a [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 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]] 2.1, 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]] 2.1 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]] 2.0 mono-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] structure is (% style="color:#e74c3c" %)mapped(%%) to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 and then the latter is (% style="color:#e74c3c" %)mapped(%%) back to [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] 2.0, the original data structure is obtained (apart from the name of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[measure>>doc:sdmx:Glossary.Measure.WebHome]], that in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 must become “obs_value”). | ||
| 303 | |||
| 304 | 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 assignmentStatus, which does not exist in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], the AttributeRelationship for the DataAttributes and so on. | ||
| 305 | |||
| 306 | ==== 10.3.4.2 Unpivot Mapping ==== | ||
| 307 | |||
| 308 | 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. | ||
| 309 | |||
| 310 | 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). For such [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures, in fact, the basic method cannot be applied, given that by maintaining the data structure unchanged the resulting [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data structure would have more than one [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]], which is not allowed by [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 (it allows just one [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]], the PrimaryMeasure, called “obs_value”). | ||
| 311 | |||
| 312 | The multi-[[measures>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures have not a [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] Identifier (because the [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] are separate [[components>>doc:sdmx:Glossary.Component.WebHome]]) and need to be 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 multiple [[measures>>doc:sdmx:Glossary.Measure.WebHome]], and an added PrimaryMeasure, in which the [[measures>>doc:sdmx:Glossary.Measure.WebHome]]’ values are maintained. | ||
| 313 | |||
| 314 | The **unpivot** mapping behaves like follows: | ||
| 315 | |||
| 316 | * 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); | ||
| 317 | * 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; | ||
| 318 | * a PrimaryMeasure [[component>>doc:sdmx:Glossary.Component.WebHome]] called “obs_value” is added to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure; | ||
| 319 | * each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] is (% style="color:#e74c3c" %)mapped(%%) to a (% style="color:#e74c3c" %)Concept(%%) 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); | ||
| 320 | * 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. | ||
| 321 | |||
| 322 | The summary mapping table of the **unpivot** mapping method is the following: | ||
| 323 | |||
| 324 | (% style="width:904.294px" %) | ||
| 325 | |(% style="width:291px" %)**VTL**|(% style="width:611px" %)**SDMX** | ||
| 326 | |(% style="width:291px" %)(Simple) Identifier|(% style="width:611px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] | ||
| 327 | |(% style="width:291px" %)(Time) Identifier|(% style="width:611px" %)TimeDimension | ||
| 328 | |(% style="width:291px" %)All [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[Components>>doc:sdmx:Glossary.Component.WebHome]]|(% style="width:611px" %)((( | ||
| 329 | MeasureDimension (having one [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] (% style="color:#e74c3c" %)Concept(%%) for each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]]) & PrimaryMeasure | ||
| 330 | ))) | ||
| 331 | |(% style="width:291px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]] |(% style="width:611px" %)((( | ||
| 332 | 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 | ||
| 333 | ))) | ||
| 334 | |||
| 335 | At observation / data point (% style="color:#e74c3c" %)level(%%): | ||
| 336 | |||
| 337 | * 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]] | ||
| 338 | * 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]] [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]], for all the observations of the set above | ||
| 339 | * 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 value of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension of the j^^th^^ observation of the set (i.e. the (% style="color:#e74c3c" %)Concept(%%) Cj) | ||
| 340 | * 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]] PrimaryMeasure of the j^^th^^ observation of the set | ||
| 341 | * 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) | ||
| 342 | |||
| 343 | 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. | ||
| 344 | |||
| 345 | Like in the general case, a MeasureDimension [[component>>doc:sdmx:Glossary.Component.WebHome]] called “measure_name” would be added to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure and would have just one possible [[measure>>doc:sdmx:Glossary.Measure.WebHome]] (% style="color:#e74c3c" %)concept(%%), corresponding to 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]] [[component>>doc:sdmx:Glossary.Component.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 [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] PrimaryMeasure called “obs_value”. | ||
| 346 | |||
| 347 | 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 (% style="color:#e74c3c" %)Concepts(%%) 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]] ConceptScheme, 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 assignmentStatus, which does not exist in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], the attributeRelationship for the DataAttributes and so on. | ||
| 348 | |||
| 349 | ==== 10.3.4.3 From VTL Measures to SDMX Data Attributes** ** ==== | ||
| 350 | |||
| 351 | 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 one [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[measure>>doc:sdmx:Glossary.Measure.WebHome]] in the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] primaryMeasure 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”). | ||
| 352 | |||
| 353 | When applied to mono-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures (having one [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]]), the M2A method behaves like the Basic mapping (the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] [[component>>doc:sdmx:Glossary.Component.WebHome]] becomes the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] primary [[measure>>doc:sdmx:Glossary.Measure.WebHome]] “obs_value”, there is no additional [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[measure>>doc:sdmx:Glossary.Measure.WebHome]] to be converted to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute). Therefore the mapping table is the same as for the Basic method: | ||
| 354 | |||
| 355 | (% style="width:591.294px" %) | ||
| 356 | |(% style="width:252px" %)**VTL**|(% style="width:336px" %)**SDMX** | ||
| 357 | |(% style="width:252px" %)(Simple) Identifier|(% style="width:336px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] | ||
| 358 | |(% style="width:252px" %)(Time) Identifier|(% style="width:336px" %)TimeDimension | ||
| 359 | |(% style="width:252px" %)([[Measure>>doc:sdmx:Glossary.Measure.WebHome]]) Identifier (if any)|(% style="width:336px" %)MeasureDimension | ||
| 360 | |(% style="width:252px" %)[[Measure>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:336px" %)PrimaryMeasure | ||
| 361 | |(% style="width:252px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]|(% style="width:336px" %)DataAttribute | ||
| 362 | |||
| 363 | For 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]]), one [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] becomes the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] PrimaryMeasure while the other [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:sdmx:Glossary.Measure.WebHome]] maintain their names and values but assume the role of DataAttribute in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]. The choice of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:sdmx:Glossary.Measure.WebHome]] that correspond to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] PrimaryMeasure is left to the definer of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[data structure definition>>doc:sdmx:Glossary.Data structure definition.WebHome]]. | ||
| 364 | |||
| 365 | Taking into account that the multi-[[measure>>doc:sdmx:Glossary.Measure.WebHome]] [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] structures do not have a [[measure>>doc:sdmx:Glossary.Measure.WebHome]] identifier, the mapping table is the following: | ||
| 366 | |||
| 367 | (% style="width:588.294px" %) | ||
| 368 | |(% style="width:259px" %)**VTL**|(% style="width:326px" %)**SDMX** | ||
| 369 | |(% style="width:259px" %)(Simple) Identifier|(% style="width:326px" %)[[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] | ||
| 370 | |(% style="width:259px" %)(Time) Identifier|(% style="width:326px" %)TimeDimension | ||
| 371 | |(% style="width:259px" %)One of the [[Measures>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:326px" %)PrimaryMeasure | ||
| 372 | |(% style="width:259px" %)Other [[Measures>>doc:sdmx:Glossary.Measure.WebHome]]|(% style="width:326px" %)DataAttribute | ||
| 373 | |(% style="width:259px" %)[[Attribute>>doc:sdmx:Glossary.Attribute.WebHome]]|(% style="width:326px" %)DataAttribute | ||
| 374 | |||
| 375 | 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 assignmentStatus, which does not exist in [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]], the attributeRelationship for the DataAttributes and so on. In particular, the primaryMeasure of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 [[DSD>>doc:sdmx:Glossary.Data structure definition.WebHome]] must be called “obs_value” and must be one of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:sdmx:Glossary.Measure.WebHome]], chosen by the [[DSD>>doc:sdmx:Glossary.Data structure definition.WebHome]] definer. | ||
| 376 | |||
| 377 | === 10.3.5 Declaration of the mapping methods between data structures === | ||
| 378 | |||
| 379 | 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. | ||
| 380 | |||
| 381 | 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. | ||
| 382 | |||
| 383 | 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]]. | ||
| 384 | |||
| 385 | The VtlMappingScheme is a container for zero or more VtlDataflowMapping (besides possible mappings to [[artefacts>>doc:sdmx:Glossary.Artefact.WebHome]] other than [[dataflows>>doc:sdmx:Glossary.Dataflow.WebHome]]). | ||
| 386 | |||
| 387 | === 10.3.6 Mapping dataflow subsets to distinct VTL data sets{{footnote}}The kind of mapping explained here works in combination with a SDMX specific naming convention that requires pre-processing before parsing the VTL expressions. As highlighted below, the identifiers of the VTL datasets are a shortcut of some specific VTL operators applied to the SDMX Dataflows. This is not safe to use outside an SDMX context, as the naming convention may have no meaning there.{{/footnote}} === | ||
| 388 | |||
| 389 | Until now it as 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]] [[dataset>>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]]). | ||
| 390 | |||
| 391 | 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 dimension components of the Dataflow except the time Dimension. 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}} | ||
| 392 | |||
| 393 | 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 datasets.{{/footnote}} | ||
| 394 | |||
| 395 | 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]]. | ||
| 396 | |||
| 397 | For example, assuming that the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] [[dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] DF1(1.0) 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). | ||
| 398 | |||
| 399 | In practice, this kind mapping is obtained like follows: | ||
| 400 | |||
| 401 | * 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 [[dimension>>doc:sdmx:Glossary.Dimension.WebHome]] [[components>>doc:sdmx:Glossary.Component.WebHome]] 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 datasets is not used.{{/footnote}} Following the example above, imagine that the user declares the [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY. | ||
| 402 | * The [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] is given a name using a special notation also called “ordered concatenation” and composed of the following parts: | ||
| 403 | ** 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); | ||
| 404 | ** a slash (“/”) as a separator;{{footnote}}As a consequence of this formalism, a slash in the name of the VTL dataset assumes the specific meaning of separator between the name of the Dataflow and the values of some of its Dimensions.{{/footnote}} | ||
| 405 | ** 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]] [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] declared above must have, separated by dots (“.”) and written in the order in which these [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] are defined{{footnote}}This is the order in which the dimensions are defined in the ToVtlSpaceKey class or in the FromVtlSpaceKey class, depending on the direction of the mapping.{{/footnote}}. For example POPULATION.USA would mean that such a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>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. | ||
| 406 | |||
| 407 | 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. | ||
| 408 | |||
| 409 | 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: | ||
| 410 | |||
| 411 | > ‘DF(1.0)///INDICATORvalue//.//COUNTRYvalue//’ | ||
| 412 | |||
| 413 | Where DF(1.0) is the [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] and //INDICATORvalue// and //COUNTRYvalue //are placeholders for one value of the INDICATOR and COUNTRY dimensions. | ||
| 414 | |||
| 415 | 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: | ||
| 416 | |||
| 417 | > ‘DF(1.0)/POPULATION.USA’ | ||
| 418 | |||
| 419 | 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) for which //INDICATOR// = POPULATION and //COUNTRY// = USA. | ||
| 420 | |||
| 421 | 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]]. | ||
| 422 | |||
| 423 | 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 [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.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]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] are result of [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] transformation{{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}} and 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. | ||
| 424 | |||
| 425 | 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)) need to be (% style="color:#e74c3c" %)mapped(%%) to distinct [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] that are operand of some [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] transformations. | ||
| 426 | |||
| 427 | As already said, each [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] is assumed to contain all the observations of the [[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)/POPULATION.USA’ would contain all the observations of DF1(1.0) having INDICATOR = POPULATION and COUNTRY = USA. | ||
| 428 | |||
| 429 | In order to obtain the data structure of these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>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]] [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] 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]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] {{footnote}}If these dimensions would not be dropped, taking into account that the typical binary VTL operations at dataset level (+, -, *, / and so on) are executed on the observations having matching identifiers, the VTL datasets resulting from this kind of mapping would have non-matching values for the mapping dimensions (e.g. POPULATION and COUNTRY), therefore 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) is applied (i.e. basic, pivot …). | ||
| 430 | |||
| 431 | In the example above, for all the [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] of the kind ‘DF1(1.0)///INDICATORvalue//.//COUNTRYvalue//’, the [[dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY would be dropped so that the data structure of all the resulting [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[data sets>>doc:sdmx:Glossary.Data set.WebHome]] would have the identifier TIME_PERIOD only. | ||
| 432 | |||
| 433 | It should be noted that the desired [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] (i.e. of the kind ‘DF1(1.0)/// 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), like in the following [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] expression: | ||
| 434 | |||
| 435 | > ‘DF1(1.0)/POPULATION.USA’ := | ||
| 436 | > DF1(1.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“USA” ]; | ||
| 437 | > ‘DF1(1.0)/POPULATION.CANADA’ := | ||
| 438 | > DF1(1.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“CANADA” ]; | ||
| 439 | > … … … | ||
| 440 | |||
| 441 | 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]] [[datasets>>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 and, 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}} | ||
| 442 | |||
| 443 | 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 [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] 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. | ||
| 444 | |||
| 445 | For example, ‘DF(1.0)/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) for which //INDICATOR// = POPULATION and COUNTRY = any value. | ||
| 446 | |||
| 447 | This is equivalent to the application of the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] “sub” operator only to the identifier //INDICATOR//: | ||
| 448 | |||
| 449 | > ‘DF1(1.0)/POPULATION.’ := | ||
| 450 | > DF1(1.0) [sub INDICATOR=“POPULATION” ]; | ||
| 451 | |||
| 452 | Therefore the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:sdmx:Glossary.Data set.WebHome]] ‘DF1(1.0)/POPULATION.’ would have the identifiers COUNTRY and TIME_PERIOD. | ||
| 453 | |||
| 454 | 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. | ||
| 455 | |||
| 456 | Let us now analyse the __mapping direction from [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]__. | ||
| 457 | |||
| 458 | 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. | ||
| 459 | |||
| 460 | 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) 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) that have different combinations of values for INDICATOR and COUNTRY: | ||
| 461 | |||
| 462 | * each part is calculated as a [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] derived [[dataset>>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}} | ||
| 463 | * the data structure of all these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>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}}. | ||
| 464 | * In fact the VTL operator “sub” has exactly the same behaviour. Therefore, Under these hypothesis, such derived [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:sdmx:Glossary.Data set.WebHome]] can be (% style="color:#e74c3c" %)mapped(%%) to DF2(1.0) by declaring the [[Dimensions>>doc:sdmx:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY as 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}} | ||
| 465 | |||
| 466 | 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:{{footnote}}the symbol of the VTL persistent assignment is used (<-){{/footnote}} | ||
| 467 | |||
| 468 | ‘DF2(1.0)///INDICATORvalue//.//COUNTRYvalue//’ <- expression | ||
| 469 | |||
| 470 | Some examples follow, for some specific values of INDICATOR and COUNTRY: | ||
| 471 | |||
| 472 | ‘DF2(1.0)/GDPPERCAPITA.USA’ <- expression11; | ||
| 473 | ‘DF2(1.0)/GDPPERCAPITA.CANADA’ <- expression12; | ||
| 474 | … … … | ||
| 475 | ‘DF2(1.0)/POPGROWTH.USA’ <- expression21; | ||
| 476 | ‘DF2(1.0)/POPGROWTH.CANADA’ <- expression22; | ||
| 477 | |||
| 478 | … … … | ||
| 479 | |||
| 480 | As said, it is assumed that these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] derived [[datasets>>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: | ||
| 481 | |||
| 482 | [[image:1747859458410-183.png||height="170" width="663"]] | ||
| 483 | |||
| 484 | 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)), that 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]]. Following the same example, these [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] transformations would be: | ||
| 485 | |||
| 486 | [[image:1747859612718-454.png||height="451" width="602"]] | ||
| 487 | |||
| 488 | 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. | ||
| 489 | |||
| 490 | 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}} | ||
| 491 | |||
| 492 | 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). | ||
| 493 | |||
| 494 | === 10.3.7 Mapping variables and value domains between VTL and SDMX === | ||
| 495 | |||
| 496 | 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: | ||
| 497 | |||
| 498 | (% style="width:890.835px" %) | ||
| 499 | |(% style="width:314px" %)VTL|(% style="width:574px" %)SDMX | ||
| 500 | |(% style="width:314px" %)**[[Data Set>>doc:sdmx:Glossary.Data set.WebHome]] [[Component>>doc:sdmx:Glossary.Component.WebHome]]**|(% style="width:574px" %)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 [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]] or a PrimaryMeasure or a DataAttribute) belonging to one specific [[Dataflow>>doc:sdmx:Glossary.Dataflow.WebHome]] {{footnote}}Through SDMX Constraints, it is possible to specify the values that a Component of a Dataflow can assume.{{/footnote}} | ||
| 501 | |(% style="width:314px" %)**Represented Variable**|(% style="width:574px" %)(% style="color:#e74c3c" %)**Concept**(%%) with a definite [[Representation>>doc:sdmx:Glossary.Representation.WebHome]] | ||
| 502 | |(% style="width:314px" %)**Value Domain**|(% style="width:574px" %)**[[Representation>>doc:sdmx:Glossary.Representation.WebHome]]** (see the Structure Pattern in the Base Package) | ||
| 503 | |(% style="width:314px" %)**Enumerated Value Domain / [[Code List>>doc:sdmx:Glossary.Code list.WebHome]]**|(% style="width:574px" %)((( | ||
| 504 | **Codelist** (for enumerated [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], PrimaryMeasure, DataAttribute) or **ConceptScheme **(for MeasureDimension) | ||
| 505 | ))) | ||
| 506 | |(% style="width:314px" %)**[[Code>>doc:sdmx:Glossary.Code.WebHome]]**|(% style="width:574px" %)**[[Code>>doc:sdmx:Glossary.Code.WebHome]]** (for enumerated [[Dimension>>doc:sdmx:Glossary.Dimension.WebHome]], PrimaryMeasure, DataAttribute) or (% style="color:#e74c3c" %)**Concept**(%%) (for MeasureDimension) | ||
| 507 | |(% style="width:314px" %)**Described Value Domain**|(% style="width:574px" %)((( | ||
| 508 | non-enumerated** [[Representation>>doc:sdmx:Glossary.Representation.WebHome]] **(having [[Facets>>doc:sdmx:Glossary.Facet.WebHome]] / ExtendedFacets, see the Structure Pattern in the Base Package) | ||
| 509 | ))) | ||
| 510 | |(% style="width:314px" %)**Value**|(% style="width:574px" %)((( | ||
| 511 | 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 to a valid **value **(for non-enumerated** **[[Representations>>doc:sdmx:Glossary.Representation.WebHome]]) or to a (% style="color:#e74c3c" %)**Concept**(%%)** **(for MeasureDimension) | ||
| 512 | ))) | ||
| 513 | |(% style="width:314px" %)**Value Domain Subset / Set**|(% style="width:574px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] | ||
| 514 | |(% style="width:314px" %)**Enumerated Value Domain Subset / Enumerated Set**|(% style="width:574px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] | ||
| 515 | |(% style="width:314px" %)**Described Value Domain Subset / Described Set**|(% style="width:574px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] | ||
| 516 | |(% style="width:314px" %)**Set list**|(% style="width:574px" %)This abstraction does not exist in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] | ||
| 517 | |||
| 518 | 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). | ||
| 519 | |||
| 520 | 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). | ||
| 521 | |||
| 522 | 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. | ||
| 523 | |||
| 524 | 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 | ||
| 525 | |||
| 526 | DS_c := DS_a + DS_b (where DS_a, DS_b, DS_c are VTL Data Sets) | ||
| 527 | |||
| 528 | 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. | ||
| 529 | |||
| 530 | 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]] 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(%%). | ||
| 531 | |||
| 532 | 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. ISO-alpha-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. | ||
| 533 | |||
| 534 | == 10.4 Mapping between SDMX and VTL Data Types == | ||
| 535 | |||
| 536 | === 10.4.1 VTL Data types === | ||
| 537 | |||
| 538 | 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 compiletime errors. | ||
| 539 | |||
| 540 | 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: | ||
| 541 | |||
| 542 | [[image:1747836776716-178.png]] | ||
| 543 | |||
| 544 | **Figure 12 – VTL Data Types** | ||
| 545 | |||
| 546 | 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. | ||
| 547 | |||
| 548 | 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): | ||
| 549 | |||
| 550 | [[image:1747859722732-549.png||height="283" width="224"]] | ||
| 551 | |||
| 552 | **Figure 13 – VTL Basic Scalar Types** | ||
| 553 | |||
| 554 | === 10.4.2 VTL basic scalar types and SDMX data types === | ||
| 555 | |||
| 556 | 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]]. | ||
| 557 | |||
| 558 | 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-MM-GG and MM-GG-YYYY (e.g. respectively 2010-12-31 and 1231-2010). | ||
| 559 | |||
| 560 | 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). | ||
| 561 | |||
| 562 | 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. | ||
| 563 | |||
| 564 | [[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). | ||
| 565 | |||
| 566 | 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. | ||
| 567 | |||
| 568 | 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. | ||
| 569 | |||
| 570 | 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]]. | ||
| 571 | |||
| 572 | === 10.4.3 Mapping SDMX data types to VTL basic scalar types === | ||
| 573 | |||
| 574 | 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. | ||
| 575 | |||
| 576 | (% style="width:653.835px" %) | ||
| 577 | |(% style="width:366px" %)**SDMX data type (BasicComponentDataType)**|(% style="width:284px" %)**Default [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar type** | ||
| 578 | |(% style="width:366px" %)((( | ||
| 579 | **String** | ||
| 580 | (string allowing any character) | ||
| 581 | )))|(% style="width:284px" %)**string** | ||
| 582 | |(% style="width:366px" %)((( | ||
| 583 | **Alpha** | ||
| 584 | (string which only allows A-z) | ||
| 585 | )))|(% style="width:284px" %)**string** | ||
| 586 | |(% style="width:366px" %)((( | ||
| 587 | **AlphaNumeric** | ||
| 588 | (string which only allows A-z and 0-9) | ||
| 589 | )))|(% style="width:284px" %)**string** | ||
| 590 | |(% style="width:366px" %)((( | ||
| 591 | **Numeric** | ||
| 592 | (string which only allows 0-9, but is not numeric so that is can having leading zeros) | ||
| 593 | )))|(% style="width:284px" %)**string** | ||
| 594 | |(% style="width:366px" %)((( | ||
| 595 | **BigInteger** | ||
| 596 | (corresponds to XML Schema xs:integer datatype; infinite set of integer values) | ||
| 597 | )))|(% style="width:284px" %)**integer** | ||
| 598 | |(% style="width:366px" %)((( | ||
| 599 | **Integer** | ||
| 600 | (corresponds to XML Schema xs:int datatype; between -2147483648 and +2147483647 (inclusive)) | ||
| 601 | )))|(% style="width:284px" %)**integer** | ||
| 602 | |(% style="width:366px" %)((( | ||
| 603 | **Long** | ||
| 604 | (corresponds to XML Schema xs:long datatype; between -9223372036854775808 and +9223372036854775807 (inclusive)) | ||
| 605 | )))|(% style="width:284px" %)**integer** | ||
| 606 | |(% style="width:366px" %)((( | ||
| 607 | **Short** | ||
| 608 | (corresponds to XML Schema xs:short datatype; between -32768 and -32767 (inclusive)) | ||
| 609 | )))|(% style="width:284px" %)**integer** | ||
| 610 | |(% style="width:366px" %)((( | ||
| 611 | **[[Decimal>>doc:sdmx:Glossary.Decimals.WebHome]]** | ||
| 612 | (corresponds to XML Schema xs:decimal datatype; subset of real numbers that can be represented as decimals) | ||
| 613 | )))|(% style="width:284px" %)**number** | ||
| 614 | |(% style="width:366px" %)((( | ||
| 615 | **Float** | ||
| 616 | (corresponds to XML Schema xs:float datatype; patterned after the IEEE single-precision 32-bit floating point type) | ||
| 617 | )))|(% style="width:284px" %)**number** | ||
| 618 | |(% style="width:366px" %)((( | ||
| 619 | **Double** | ||
| 620 | (corresponds to XML Schema xs:double datatype; patterned after the IEEE double-precision 64-bit floating point type) | ||
| 621 | )))|(% style="width:284px" %)**number** | ||
| 622 | |(% style="width:366px" %)((( | ||
| 623 | **Boolean** | ||
| 624 | (corresponds to the XML Schema xs:boolean datatype; support the mathematical (% style="color:#e74c3c" %)concept(%%) of binary-valued logic: {true, false}) | ||
| 625 | )))|(% style="width:284px" %)**boolean** | ||
| 626 | |(% style="width:366px" %)((( | ||
| 627 | **URI** | ||
| 628 | (corresponds to the XML Schema xs:anyURI; absolute or relative Uniform Resource Identifier Reference) | ||
| 629 | )))|(% style="width:284px" %)**string** | ||
| 630 | |(% style="width:366px" %)((( | ||
| 631 | **Count** | ||
| 632 | (an integer following a sequential pattern, increasing by 1 for each occurrence) | ||
| 633 | )))|(% style="width:284px" %)**integer** | ||
| 634 | |(% style="width:366px" %)((( | ||
| 635 | **InclusiveValueRange** | ||
| 636 | ([[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) | ||
| 637 | )))|(% style="width:284px" %)**number** | ||
| 638 | |(% style="width:366px" %)((( | ||
| 639 | **ExclusiveValueRange** | ||
| 640 | ([[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) | ||
| 641 | )))|(% style="width:284px" %)**number** | ||
| 642 | |(% style="width:366px" %)((( | ||
| 643 | **Incremental ** | ||
| 644 | ([[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) | ||
| 645 | )))|(% style="width:284px" %)**number** | ||
| 646 | |(% style="width:366px" %)((( | ||
| 647 | **ObservationalTimePeriod** | ||
| 648 | (superset of StandardTimePeriod and TimeRange) | ||
| 649 | )))|(% style="width:284px" %)**time** | ||
| 650 | |(% style="width:366px" %)((( | ||
| 651 | **StandardTimePeriod** | ||
| 652 | (superset of BasicTimePeriod and ReportingTimePeriod) | ||
| 653 | )))|(% style="width:284px" %)**time** | ||
| 654 | |(% style="width:366px" %)((( | ||
| 655 | **BasicTimePeriod** | ||
| 656 | (superset of GregorianTimePeriod and DateTime) | ||
| 657 | )))|(% style="width:284px" %)**date** | ||
| 658 | |(% style="width:366px" %)((( | ||
| 659 | **GregorianTimePeriod** | ||
| 660 | (superset of GregorianYear, GregorianYearMonth, and GregorianDay) | ||
| 661 | )))|(% style="width:284px" %)**date** | ||
| 662 | |(% style="width:366px" %)**GregorianYear **(YYYY)|(% style="width:284px" %)**date** | ||
| 663 | |(% style="width:366px" %)**GregorianYearMonth** / **GregorianMonth** (YYYY-MM)|(% style="width:284px" %)**date** | ||
| 664 | |(% style="width:366px" %)**GregorianDay **(YYYY-MM-DD)|(% style="width:284px" %)**date** | ||
| 665 | |(% style="width:366px" %)((( | ||
| 666 | **ReportingTimePeriod ** | ||
| 667 | (superset of RepostingYear, ReportingSemester, ReportingTrimester, ReportingQuarter, ReportingMonth, ReportingWeek, ReportingDay) | ||
| 668 | )))|(% style="width:284px" %)**time_period** | ||
| 669 | |(% style="width:366px" %)((( | ||
| 670 | **ReportingYear** | ||
| 671 | (YYYY-A1 – 1 year period) | ||
| 672 | )))|(% style="width:284px" %)**time_period** | ||
| 673 | |(% style="width:366px" %)((( | ||
| 674 | **ReportingSemester** | ||
| 675 | (YYYY-Ss – 6 month period) | ||
| 676 | )))|(% style="width:284px" %)**time_period** | ||
| 677 | |(% style="width:366px" %)((( | ||
| 678 | **ReportingTrimester** | ||
| 679 | (YYYY-Tt – 4 month period) | ||
| 680 | )))|(% style="width:284px" %)**time_period** | ||
| 681 | |(% style="width:366px" %)((( | ||
| 682 | **ReportingQuarter** | ||
| 683 | (YYYY-Qq – 3 month period) | ||
| 684 | )))|(% style="width:284px" %)**time_period** | ||
| 685 | |(% style="width:366px" %)((( | ||
| 686 | **ReportingMonth** | ||
| 687 | (YYYY-Mmm – 1 month period) | ||
| 688 | )))|(% style="width:284px" %)**time_period** | ||
| 689 | |(% style="width:366px" %)((( | ||
| 690 | **ReportingWeek** | ||
| 691 | (YYYY-Www – 7 day period; following ISO 8601 definition of a week in a year) | ||
| 692 | )))|(% style="width:284px" %)**time_period** | ||
| 693 | |(% style="width:366px" %)((( | ||
| 694 | **ReportingDay** | ||
| 695 | (YYYY-Dddd – 1 day period) | ||
| 696 | )))|(% style="width:284px" %)**time_period** | ||
| 697 | |(% style="width:366px" %)((( | ||
| 698 | **DateTime** | ||
| 699 | (YYYY-MM-DDThh:mm:ss) | ||
| 700 | )))|(% style="width:284px" %)**date** | ||
| 701 | |(% style="width:366px" %)((( | ||
| 702 | **TimeRange** | ||
| 703 | |||
| 704 | (YYYY-MM-DD(Thh:mm:ss)?/) | ||
| 705 | )))|(% style="width:284px" %)**time** | ||
| 706 | |(% style="width:366px" %)((( | ||
| 707 | **Month** | ||
| 708 | (MM; speicifies a month independent of a year; e.g. February is black history month in the United States) | ||
| 709 | )))|(% style="width:284px" %)**string** | ||
| 710 | |(% style="width:366px" %)((( | ||
| 711 | **MonthDay** | ||
| 712 | (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) | ||
| 713 | )))|(% style="width:284px" %)**string** | ||
| 714 | |(% style="width:366px" %)((( | ||
| 715 | **Day** | ||
| 716 | (-DD; specifies a day independent of a month or year; e.g. the 15^^th^^ is payday) | ||
| 717 | )))|(% style="width:284px" %)**string** | ||
| 718 | |(% style="width:366px" %)((( | ||
| 719 | **Time** | ||
| 720 | (hh:mm:ss; time independent of a date; e.g. coffee break is at 10:00 AM) | ||
| 721 | )))|(% style="width:284px" %)**string** | ||
| 722 | |(% style="width:366px" %)((( | ||
| 723 | **Duration** | ||
| 724 | (corresponds to XML Schema xs:duration datatype) | ||
| 725 | )))|(% style="width:284px" %)**duration** | ||
| 726 | |(% style="width:366px" %)XHTML|(% style="width:284px" %)Metadata type – not applicable | ||
| 727 | |(% style="width:366px" %)KeyValues|(% style="width:284px" %)Metadata type – not applicable | ||
| 728 | |(% style="width:366px" %)IdentifiableReference|(% style="width:284px" %)Metadata type – not applicable | ||
| 729 | |(% style="width:366px" %)DataSetReference|(% style="width:284px" %)Metadata type – not applicable | ||
| 730 | |(% style="width:366px" %)AttachmentConstraintReference|(% style="width:284px" %)Metadata type – not applicable | ||
| 731 | |||
| 732 | **Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types** | ||
| 733 | |||
| 734 | 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). | ||
| 735 | |||
| 736 | === 10.4.4 Mapping VTL basic scalar types to SDMX data types === | ||
| 737 | |||
| 738 | The following table describes the default conversion from the [[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] basic scalar types to the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] data types . | ||
| 739 | |||
| 740 | (% style="width:923.835px" %) | ||
| 741 | |(% style="width:191px" %)**VTL basic scalar type**|(% style="width:419px" %)**Default SDMX data type (BasicComponentDataType)**|(% style="width:311px" %)**Default output format** | ||
| 742 | |(% style="width:191px" %)**String**|(% style="width:419px" %)**String **|(% style="width:311px" %)Like XML (xs:string) | ||
| 743 | |(% style="width:191px" %)**Number**|(% style="width:419px" %)**Float **|(% style="width:311px" %)Like XML (xs:float) | ||
| 744 | |(% style="width:191px" %)**Integer**|(% style="width:419px" %)**Integer **|(% style="width:311px" %)Like XML (xs:int) | ||
| 745 | |(% style="width:191px" %)**Date**|(% style="width:419px" %)**DateTime**|(% style="width:311px" %)YYYY-MM-DDT00:00:00Z | ||
| 746 | |(% style="width:191px" %)**Time**|(% style="width:419px" %)**StandardTimePeriod**|(% style="width:311px" %)/ (as defined above) | ||
| 747 | |(% style="width:191px" %)**time_period**|(% style="width:419px" %)((( | ||
| 748 | **ReportingTimePeriod | ||
| 749 | (StandardReportingPeriod)** | ||
| 750 | )))|(% style="width:311px" %)((( | ||
| 751 | YYYY-Pppp | ||
| 752 | (according to [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] ) | ||
| 753 | ))) | ||
| 754 | |(% style="width:191px" %)**Duration**|(% style="width:419px" %)**Duration **|(% style="width:311px" %)((( | ||
| 755 | Like XML (xs:duration) | ||
| 756 | PnYnMnDTnHnMnS | ||
| 757 | ))) | ||
| 758 | |(% style="width:191px" %)**Boolean**|(% style="width:419px" %)**Boolean **|(% style="width:311px" %)((( | ||
| 759 | Like XML (xs:boolean) with the values “true” or “false” | ||
| 760 | ))) | ||
| 761 | |||
| 762 | **Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types** | ||
| 763 | |||
| 764 | 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 information model>>doc:sdmx:Glossary.SDMX Information Model.WebHome]]). | ||
| 765 | |||
| 766 | 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. | ||
| 767 | |||
| 768 | (% style="width:671.835px" %) | ||
| 769 | |(% colspan="2" style="width:669px" %)**VTL special characters for the formatting masks** | ||
| 770 | |(% colspan="2" style="width:669px" %)** ** | ||
| 771 | |(% colspan="2" style="width:669px" %)**Number ** | ||
| 772 | |(% style="width:141px" %)D|(% style="width:528px" %)one numeric digit (if the scientific notation is adopted, D is only for the mantissa) | ||
| 773 | |(% style="width:141px" %)E|(% style="width:528px" %)one numeric digit (for the exponent of the scientific notation) | ||
| 774 | |(% style="width:141px" %).(dot)|(% style="width:528px" %)possible separator between the integer and the [[decimal>>doc:sdmx:Glossary.Decimals.WebHome]] parts. | ||
| 775 | |(% style="width:141px" %),(comma)|(% style="width:528px" %)possible separator between the integer and the [[decimal>>doc:sdmx:Glossary.Decimals.WebHome]] parts. | ||
| 776 | |(% style="width:141px" %) |(% style="width:528px" %) | ||
| 777 | |(% colspan="2" style="width:669px" %)**Time and duration** | ||
| 778 | |(% style="width:141px" %)C |(% style="width:528px" %)century | ||
| 779 | |(% style="width:141px" %)Y|(% style="width:528px" %)year | ||
| 780 | |(% style="width:141px" %)S|(% style="width:528px" %)semester | ||
| 781 | |(% style="width:141px" %)Q|(% style="width:528px" %)quarter | ||
| 782 | |(% style="width:141px" %)M|(% style="width:528px" %)month | ||
| 783 | |(% style="width:141px" %)W|(% style="width:528px" %)week | ||
| 784 | |(% style="width:141px" %)D|(% style="width:528px" %)day | ||
| 785 | |(% style="width:141px" %)h |(% style="width:528px" %)hour digit (by default on 24 hours) | ||
| 786 | |(% style="width:141px" %)M|(% style="width:528px" %)minute | ||
| 787 | |(% style="width:141px" %)S|(% style="width:528px" %)second | ||
| 788 | |(% style="width:141px" %)D|(% style="width:528px" %)[[decimal>>doc:sdmx:Glossary.Decimals.WebHome]] of second | ||
| 789 | |(% style="width:141px" %)P|(% style="width:528px" %)period indicator (representation in one digit for the duration) | ||
| 790 | |(% style="width:141px" %)P|(% style="width:528px" %)number of the periods specified in the period indicator | ||
| 791 | |(% style="width:141px" %)AM/PM |(% style="width:528px" %)indicator of AM / PM (e.g. am/pm for “am” or “pm”) | ||
| 792 | |(% style="width:141px" %)MONTH|(% style="width:528px" %)uppercase textual representation of the month (e.g., JANUARY for January) | ||
| 793 | |(% style="width:141px" %)DAY|(% style="width:528px" %)uppercase textual representation of the day (e.g., MONDAY for Monday) | ||
| 794 | |(% style="width:141px" %)Month|(% style="width:528px" %)lowercase textual representation of the month (e.g., january) | ||
| 795 | |(% style="width:141px" %)Day|(% style="width:528px" %)lowercase textual representation of the month (e.g., monday) | ||
| 796 | |(% style="width:141px" %)Month|(% style="width:528px" %)First character uppercase, then lowercase textual representation of the month (e.g., January) | ||
| 797 | |(% style="width:141px" %)Day|(% style="width:528px" %)First character uppercase, then lowercase textual [[representation>>doc:sdmx:Glossary.Representation.WebHome]] of the day using (e.g. Monday) | ||
| 798 | |(% style="width:141px" %) |(% style="width:528px" %) | ||
| 799 | |(% colspan="2" style="width:669px" %)**String** | ||
| 800 | |(% style="width:141px" %)X|(% style="width:528px" %)any string character | ||
| 801 | |(% style="width:141px" %)Z|(% style="width:528px" %)any string character from “A” to “z” | ||
| 802 | |(% style="width:141px" %)9|(% style="width:528px" %)any string character from “0” to “9” | ||
| 803 | |(% style="width:141px" %) |(% style="width:528px" %) | ||
| 804 | |(% colspan="2" style="width:669px" %)**Boolean** | ||
| 805 | |(% style="width:141px" %)B|(% style="width:528px" %)Boolean using “true” for True and “false” for False | ||
| 806 | |(% style="width:141px" %)1|(% style="width:528px" %)Boolean using “1” for True and “0” for False | ||
| 807 | |(% style="width:141px" %)0|(% style="width:528px" %)Boolean using “0” for True and “1” for False | ||
| 808 | |(% style="width:141px" %) |(% style="width:528px" %) | ||
| 809 | |(% colspan="2" style="width:669px" %)Other qualifiers | ||
| 810 | |(% style="width:141px" %)*|(% style="width:528px" %)an arbitrary number of digits (of the preceding type) | ||
| 811 | |(% style="width:141px" %)+|(% style="width:528px" %)at least one digit (of the preceding type) | ||
| 812 | |(% style="width:141px" %)( )|(% style="width:528px" %)optional digits (specified within the brackets) | ||
| 813 | |(% style="width:141px" %)\|(% style="width:528px" %)prefix for the special characters that must appear in the mask | ||
| 814 | |(% style="width:141px" %)N|(% style="width:528px" %)fixed number of digits used in the preceding textual [[representation>>doc:sdmx:Glossary.Representation.WebHome]] of the month or the day | ||
| 815 | |(% style="width:141px" %) |(% style="width:528px" %) | ||
| 816 | |||
| 817 | 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}}. | ||
| 818 | |||
| 819 | === 10.4.5 Null Values === | ||
| 820 | |||
| 821 | 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. | ||
| 822 | |||
| 823 | 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]]. | ||
| 824 | |||
| 825 | 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. | ||
| 826 | |||
| 827 | === 10.4.6 Format of the literals used in VTL transformations === | ||
| 828 | |||
| 829 | 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. | ||
| 830 | |||
| 831 | 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 201001-02 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. | ||
| 832 | |||
| 833 | 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. | ||
| 834 | |||
| 835 | 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]]). | ||
| 836 | |||
| 837 | 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. | ||
| 838 | |||
| 839 | 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. | ||
| 840 | |||
| 841 | = 11 Annex I: How to eliminate extra element in the .NET SDMX Web Service = | ||
| 842 | |||
| 843 | == 11.1 Problem statement == | ||
| 844 | |||
| 845 | For implementing an [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] compliant Web Service the standardised WSDL file should be used that describes the expected request/response structure. The request message of the operation contains a wrapper element (e.g. “GetGenericData”) that wraps a tag called “GenericDataQuery”, which is the actual [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] query XML message that contains the query to be processed by the Web Service. In the same way the response is formulated in a wrapper element “GetGenericDataResponse”. | ||
| 846 | |||
| 847 | As defined in the SOAP specification, the root element of a SOAP message is the Envelope, which contains an optional Header and a mandatory Body. These are illustrated below along with the Body contents according to the WSDL: | ||
| 848 | |||
| 849 | [[image:1747854006117-843.png]] | ||
| 850 | |||
| 851 | The problem that initiated the present analysis refers to the difference in the way SOAP requests are when trying to implement the aforementioned Web Service in .NET framework. | ||
| 852 | |||
| 853 | Building such a Web Service using the .NET framework is done by exposing a method (i.e. the getGenericData in the example) with an XML document argument (lets name it “Query”). **The difference that appears in Microsoft .Net implementations is that there is a need for an extra XML container around the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] GenericDataQuery.** This is the expected behavior since the framework is let to publish automatically the Web Service as a remote procedure call, thus wraps each parameter into an extra element. The .NET request is illustrated below: | ||
| 854 | |||
| 855 | [[image:1747854039499-443.png]] | ||
| 856 | |||
| 857 | [[image:1747854067769-691.png]] | ||
| 858 | |||
| 859 | Furthermore this extra element is also inserted in the automatically generated WSDL from the framework. Therefore this particularity requires custom clients for the .NET Web Services that is not an interoperable solution. | ||
| 860 | |||
| 861 | == 11.2 Solution == | ||
| 862 | |||
| 863 | The solution proposed for conforming the .NET implementation to the envisioned SOAP requests has to do with the manual intervention to the serialisation and deserialisation of the XML payloads. Since it is a Web Service of already prepared XML messages requests/responses this is the indicate way so as to have full control on the XML messages. This is the way the Java implementation (using Apache Axis) of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Web Service has adopted. | ||
| 864 | |||
| 865 | As regards the .NET platform this is related with the usage of **XmlAnyElement** parameter for the .NET web methods. | ||
| 866 | |||
| 867 | Web methods use XmlSerializer in the .NET Framework to invoke methods and build the response. | ||
| 868 | |||
| 869 | [[image:1747836776717-914.jpeg]] | ||
| 870 | |||
| 871 | The XML is passed to the XmlSerializer to de-serialize it into the instances of classes in managed [[code>>doc:sdmx:Glossary.Code.WebHome]] that (% style="color:#e74c3c" %)map(%%) to the input parameters for the Web method. Likewise, the output parameters and return values of the Web method are serialized into XML in order to create the body of the SOAP response message. | ||
| 872 | |||
| 873 | In case the developer wants more control over the serialization and de-serialization process a solution is represented by the usage of **XmlElement** parameters. This offers the opportunity of validating the XML against a schema before de-serializing it, avoiding de-serialization in the first place, analyzing the XML to determine how you want to de-serialize it, or using the many powerful XML APIs that are available to deal with the XML directly. This also gives the developer the control to handle errors in a particular way instead of using the faults that the XmlSerializer might generate under the covers. | ||
| 874 | |||
| 875 | In order to control the de-serialization process of the XmlSerializer for a Web method, **XmlAnyElement** is a simple solution to use. | ||
| 876 | |||
| 877 | To understand how the **XmlAnyElement** [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]] works we present the following two web methods: | ||
| 878 | |||
| 879 | [[image:1747854096778-844.png]] | ||
| 880 | |||
| 881 | In this method the **input** parameter is decorated with the **XmlAnyElement** parameter. This is a hint that this parameter will be de-serialized from an **xsd:any** element. Since the [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]] is not passed any parameters, it means that the entire XML element for this parameter in the SOAP message will be in the Infoset that is represented by this **XmlElement** parameter. | ||
| 882 | |||
| 883 | [[image:1747854127303-270.png]] | ||
| 884 | |||
| 885 | The difference between the two is that for the first method, **SubmitXml**, the XmlSerializer will expect an element named **input** to be an immediate child of the **SubmitXml** element in the SOAP body. The second method, **SubmitXmlAny**, will not care what the name of the child of the **SubmitXmlAny** element is. It will plug whatever XML is included into the input parameter. The message style from ASP.NET Help for the two methods is shown below. First we look at the message for the method without the **XmlAnyElement** [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]]. | ||
| 886 | |||
| 887 | [[image:1747854163928-581.png]] | ||
| 888 | |||
| 889 | Now we look at the message for the method that uses the **XmlAnyElement** [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]]. | ||
| 890 | |||
| 891 | [[image:1747854190641-364.png]] | ||
| 892 | |||
| 893 | [[image:1747854236732-512.png]] | ||
| 894 | |||
| 895 | The method decorated with the **XmlAnyElement** [[attribute>>doc:sdmx:Glossary.Attribute.WebHome]] has one fewer wrapping elements. Only an element with the name of the method wraps what is passed to the **input** parameter. | ||
| 896 | |||
| 897 | For more information please consult: [[http:~~/~~/msdn.microsoft.com/en-us/library/aa480498.aspx>>http://msdn.microsoft.com/en-us/library/aa480498.aspx]] | ||
| 898 | |||
| 899 | Furthermore at this point the problem with the different requests has been solved. However there is still the difference in the produced WSDL that has to be taken care. The automatic generated WSDL now doesn’t insert the extra element, but defines the content of the operation wrapper element as “xsd:any” type. | ||
| 900 | |||
| 901 | [[image:1747854286398-614.png]] | ||
| 902 | |||
| 903 | Without a common WSDL still the solution doesn’t enforce interoperability. In order to | ||
| 904 | |||
| 905 | “fix” the WSDL, there two approaches. The first is to intervene in the generation process. This is a complicated approach, compared to the second approach, which overrides the generation process and returns the envisioned WSDL for the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Web Service. | ||
| 906 | |||
| 907 | This is done by redirecting the request to the “/Service?WSDL” to the envisioned WSDL stored locally into the application. To do this, from the project add a “Global Application Class” item (.asax file) and override the request in the “Application_BeginRequest” method. This is demonstrated in detail in the next section. | ||
| 908 | |||
| 909 | This approach has the disadvantage that for each deployment the WSDL end point has to be changed to reflect the current URL. However this inconvenience can be easily eliminated if a developer implements a simple rewriting module for changing the end point to the one of the current deployment. | ||
| 910 | |||
| 911 | == 11.3 Applying the solution == | ||
| 912 | |||
| 913 | In the context of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Web Service, applying the above solution translates into the following: | ||
| 914 | |||
| 915 | [[image:1747854385465-132.png]] | ||
| 916 | |||
| 917 | The SOAP request/response will then be as follows: | ||
| 918 | |||
| 919 | **GenericData Request** | ||
| 920 | |||
| 921 | [[image:1747854406014-782.png]] | ||
| 922 | |||
| 923 | **GenericData Response** | ||
| 924 | |||
| 925 | [[image:1747854424488-855.png]] | ||
| 926 | |||
| 927 | For overriding the automatically produced WSDL, in the solution explorer right click the project and select “Add” -> “New item…”. Then select the “Global Application Class”. This will create “.asax” class file in which the following [[code>>doc:sdmx:Glossary.Code.WebHome]] should replace the existing empty method: | ||
| 928 | |||
| 929 | [[image:1747854453895-524.png]] | ||
| 930 | |||
| 931 | [[image:1747854476631-125.png]] | ||
| 932 | |||
| 933 | The SDMX_WSDL.wsdl should reside in the in the root directory of the application. After applying this solution the returned WSDL is the envisioned. Thus in the request message definition contains: | ||
| 934 | |||
| 935 | [[image:1747854493363-776.png]] | ||
| 936 | |||
| 937 | |||
| 938 | {{putFootnotes/}} |