Changes for page 12 Validation and Transformation Language (VTL)

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From 7.2 to 7.1 From 8.1 to 7.5

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@@ -286,62 +286,62 @@
  |(% style="width:272px" %)Measure|(% style="width:392px" %)Measure
  |(% style="width:272px" %)Attribute|(% style="width:392px" %)DataAttribute
--If the distinction between simple identifier and time identifier is not maintained in the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] environment, the classification between [[Dimension>>doc:xwiki:Glossary.Dimension.WebHome]] and TimeDimension exists only in [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]], as declared in the relevant DataStructureDefinition.
++If the distinction between simple identifier and time identifier is not maintained in the VTL environment, the classification between Dimension and TimeDimension exists only in SDMX, as declared in the relevant DataStructureDefinition.
--Regarding the [[Attributes>>doc:xwiki:Glossary.Attribute.WebHome]], because [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] considers all of them "at observation (% style="color:#2ecc71" %)level(%%)", the corresponding [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes should be put "at observation (% style="color:#2ecc71" %)level(%%) as well, unless some different information about their AttributeRelationship is otherwise available.
++Regarding the Attributes, because VTL considers all of them "at observation level", the corresponding SDMX DataAttributes should be put "at observation level" as well, unless some different information about their AttributeRelationship is otherwise available.
--Note that the basic mappings in the two directions (from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] and vice-versa) are (almost completely) reversible. In fact, if a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] structure is (% style="color:#2ecc71" %)mapped(%%) to a [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] structure and then the latter is (% style="color:#2ecc71" %)mapped(%%) back to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]], the resulting data structure is like the original one (apart for the AttributeRelationship, that can be different if the original [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] structure contains DataAttributes that are not at observation (% style="color:#2ecc71" %)level(%%)). In reverse order, if a [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] structure is (% style="color:#2ecc71" %)mapped(%%) to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] and then the latter is (% style="color:#2ecc71" %)mapped(%%) back to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]], the original data structure is obtained.
++Note that the basic mappings in the two directions (from SDMX to VTL and vice-versa) are (almost completely) reversible. In fact, if a SDMX structure is mapped to a VTL structure and then the latter is mapped back to SDMX, the resulting data structure is like the original one (apart for the AttributeRelationship, that can be different if the original SDMX structure contains DataAttributes that are not at observation level). In reverse order, if a VTL structure is mapped to SDMX and then the latter is mapped back to VTL, the original data structure is obtained.
--As said, the resulting [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] definitions must be compliant with the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] consistency rules. For example, the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[DSD>>doc:xwiki:Glossary.Data structure definition.WebHome]] must have the AttributeRelationship for the DataAttributes, which does not exist in [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]].
++As said, the resulting SDMX definitions must be compliant with the SDMX consistency rules. For example, the SDMX DSD must have the AttributeRelationship for the DataAttributes, which does not exist in VTL.
  ==== 12.3.4.2 Unpivot Mapping ====
--An alternative mapping method from [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] is the **Unpivot **mapping.
++An alternative mapping method from VTL to SDMX is the **Unpivot **mapping.
--Although this mapping method can be used in any case, it makes major sense in case the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] data structure has more than one [[measure>>doc:xwiki:Glossary.Measure.WebHome]] [[component>>doc:xwiki:Glossary.Component.WebHome]] (multi-[[measures>>doc:xwiki:Glossary.Measure.WebHome]] [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] structure). This is used to support the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 case of a MeasureDimension or any other [[Dimension>>doc:xwiki:Glossary.Dimension.WebHome]] acting as a list of [[Measures>>doc:xwiki:Glossary.Measure.WebHome]], under the assumptions explained in section “Pivot Mapping”.
++Although this mapping method can be used in any case, it makes major sense in case the VTL data structure has more than one measure component (multi-measures VTL structure). This is used to support the SDMX 2.1 case of a MeasureDimension or any other Dimension acting as a list of Measures, under the assumptions explained in section “Pivot Mapping”.
--The multi-[[measures>>doc:xwiki:Glossary.Measure.WebHome]] [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] structures are converted to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflows>>doc:xwiki:Glossary.Dataflow.WebHome]] having an added MeasureDimension, which disambiguates the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] multiple [[Measures>>doc:xwiki:Glossary.Measure.WebHome]], and a new [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] in place of the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] ones, containing the values of the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:xwiki:Glossary.Measure.WebHome]].
++The multi-measures VTL structures are converted to SDMX Dataflows having an added MeasureDimension, which disambiguates the VTL multiple Measures, and a new Measure in place of the VTL ones, containing the values of the VTL Measures.
  The **unpivot** mapping behaves like follows:
--* like in the basic mapping, a [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] (simple) identifier becomes a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]]
++* like in the basic mapping, a VTL (simple) identifier becomes a SDMX
--[[Dimension>>doc:xwiki:Glossary.Dimension.WebHome]] and a [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] (time) identifier becomes a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] TimeDimension (as said, a [[measure>>doc:xwiki:Glossary.Measure.WebHome]] identifier cannot exist in multi-[[measure>>doc:xwiki:Glossary.Measure.WebHome]] [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] structures);
++Dimension and a VTL (time) identifier becomes a SDMX TimeDimension (as said, a measure identifier cannot exist in multi-measure VTL structures);
--* a MeasureDimension [[component>>doc:xwiki:Glossary.Component.WebHome]] called "measure_name" is added to the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure;
--* a [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] [[component>>doc:xwiki:Glossary.Component.WebHome]] called "obs_value" is added to the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]]
++* a MeasureDimension component called "measure_name" is added to the SDMX DataStructure;
++* a Measure component called "obs_value" is added to the SDMX
  DataStructure;
--* each [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] is (% style="color:#2ecc71" %)mapped(%%) to a [[Code>>doc:xwiki:Glossary.Code.WebHome]] of the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension having the same name as the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] (therefore all the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] [[Components>>doc:xwiki:Glossary.Component.WebHome]] do not originate [[Components>>doc:xwiki:Glossary.Component.WebHome]] in the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure);
--* a [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Attribute>>doc:xwiki:Glossary.Attribute.WebHome]] becomes a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DataAttribute having AttributeRelationship referred to all the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponents including the TimeDimension and except the MeasureDimension.
++* each VTL Measure is mapped to a Code of the SDMX MeasureDimension having the same name as the VTL Measure (therefore all the VTL Measure Components do not originate Components in the SDMX DataStructure);
++* a VTL Attribute becomes a SDMX DataAttribute having AttributeRelationship referred to all the SDMX DimensionComponents including the TimeDimension and except the MeasureDimension.
  The summary mapping table of the **unpivot** mapping method is the following:
  (% style="width:994.294px" %)
  |(% style="width:306px" %)**VTL**|(% style="width:684px" %)**SDMX**
--|(% style="width:306px" %)(Simple) Identifier|(% style="width:684px" %)[[Dimension>>doc:xwiki:Glossary.Dimension.WebHome]]
++|(% style="width:306px" %)(Simple) Identifier|(% style="width:684px" %)Dimension
  |(% style="width:306px" %)(Time) Identifier|(% style="width:684px" %)TimeDimension
--|(% style="width:306px" %)All [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] [[Components>>doc:xwiki:Glossary.Component.WebHome]]|(% style="width:684px" %)MeasureDimension (having one [[Code>>doc:xwiki:Glossary.Code.WebHome]] for each [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[measure>>doc:xwiki:Glossary.Measure.WebHome]] [[component>>doc:xwiki:Glossary.Component.WebHome]]) & one [[Measure>>doc:xwiki:Glossary.Measure.WebHome]]
--|(% style="width:306px" %)[[Attribute>>doc:xwiki:Glossary.Attribute.WebHome]]|(% style="width:684px" %)DataAttribute depending on all [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] including the TimeDimension and except the MeasureDimension
++|(% style="width:306px" %)All Measure Components|(% style="width:684px" %)MeasureDimension (having one Code for each VTL measure component) & one Measure
++|(% style="width:306px" %)Attribute|(% style="width:684px" %)DataAttribute depending on all SDMX Dimensions including the TimeDimension and except the MeasureDimension
--At observation / data point (% style="color:#2ecc71" %)level(%%):
++At observation / data point level:
--* a multi-[[measure>>doc:xwiki:Glossary.Measure.WebHome]] [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] Data Point becomes a set of [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] observations, one for each [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]];
--* the values of the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] Identifiers become the values of the corresponding [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponents, for all the observations of the set above;
--* the name of the j^^th^^ [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] (e.g. “Cj”) becomes the [[Code>>doc:xwiki:Glossary.Code.WebHome]] of the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension of the j^^th^^ observation of the set;
--* the value of the j^^th^^ [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] becomes the value of the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] of the j^^th^^ observation of the set;
--* the values of the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Attributes>>doc:xwiki:Glossary.Attribute.WebHome]] become the values of the corresponding [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes (in principle for all the observations of the set above).
++* a multi-measure VTL Data Point becomes a set of SDMX observations, one for each VTL Measure;
++* the values of the VTL Identifiers become the values of the corresponding SDMX DimensionComponents, for all the observations of the set above;
++* the name of the j^^th^^ VTL Measure (e.g. “Cj”) becomes the Code of the SDMX MeasureDimension of the j^^th^^ observation of the set;
++* the value of the j^^th^^ VTL Measure becomes the value of the SDMX Measure of the j^^th^^ observation of the set;
++* the values of the VTL Attributes become the values of the corresponding SDMX DataAttributes (in principle for all the observations of the set above).
--If desired, this method can be applied also to mono-[[measure>>doc:xwiki:Glossary.Measure.WebHome]] [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] structures, provided that none of the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Components>>doc:xwiki:Glossary.Component.WebHome]] has already the role of [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] Identifier. Like in the general case, a MeasureDimension [[component>>doc:xwiki:Glossary.Component.WebHome]] called “measure_name” is added to the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DataStructure, in this case it has just one possible [[Code>>doc:xwiki:Glossary.Code.WebHome]], corresponding to the name of the unique [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]]. The original [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] would not become a [[Component>>doc:xwiki:Glossary.Component.WebHome]] in the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] data structure. The value of the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] would be assigned to the unique [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] called “obs_value”.
++If desired, this method can be applied also to mono-measure VTL structures, provided that none of the VTL Components has already the role of Measure Identifier. Like in the general case, a MeasureDimension component called “measure_name” is added to the SDMX DataStructure, in this case it has just one possible Code, corresponding to the name of the unique VTL Measure. The original VTL Measure would not become a Component in the SDMX data structure. The value of the VTL Measure would be assigned to the unique SDMX Measure called “obs_value”.
--In any case, the resulting [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] definitions must be compliant with the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] consistency rules. For example, the possible [[Codes>>doc:xwiki:Glossary.Code.WebHome]] of the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] MeasureDimension need to be listed in a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] Codelist, with proper id, agency and (% style="color:#2ecc71" %)version(%%); moreover, the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[DSD>>doc:xwiki:Glossary.Data structure definition.WebHome]] must have the AttributeRelationship for the DataAttributes, which does not exist in [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]].
++In any case, the resulting SDMX definitions must be compliant with the SDMX consistency rules. For example, the possible Codes of the SDMX MeasureDimension need to be listed in a SDMX Codelist, with proper id, agency and version; moreover, the SDMX DSD must have the AttributeRelationship for the DataAttributes, which does not exist in VTL.
  ==== 12.3.4.3 From VTL Measures to SDMX Data Attributes ====
--More than all for the multi-[[measure>>doc:xwiki:Glossary.Measure.WebHome]] [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] structures (having more than one [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] [[Component>>doc:xwiki:Glossary.Component.WebHome]]), it may happen that the [[Measures>>doc:xwiki:Glossary.Measure.WebHome]] of the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] Data Structure need to be managed as DataAttributes in [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]]. Therefore, a third mapping method consists in transforming some [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[measures>>doc:xwiki:Glossary.Measure.WebHome]] in a corresponding [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Measures>>doc:xwiki:Glossary.Measure.WebHome]] and all the other [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:xwiki:Glossary.Measure.WebHome]] in [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes. This method is called M2A (“M2A” stands for “[[Measures>>doc:xwiki:Glossary.Measure.WebHome]] to DataAttributes”).
++More than all for the multi-measure VTL structures (having more than one Measure Component), it may happen that the Measures of the VTL Data Structure need to be managed as DataAttributes in SDMX. Therefore, a third mapping method consists in transforming some VTL measures in a corresponding SDMX Measures and all the other VTL Measures in SDMX DataAttributes. This method is called M2A (“M2A” stands for “Measures to DataAttributes”).
--All [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measures>>doc:xwiki:Glossary.Measure.WebHome]] maintain their names in [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]]. The [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Measure>>doc:xwiki:Glossary.Measure.WebHome]] [[Components>>doc:xwiki:Glossary.Component.WebHome]] that become [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DataAttributes are the ones declared as DataAttributes in the target [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] data structure definition.
++All VTL Measures maintain their names in SDMX. The VTL Measure Components that become SDMX DataAttributes are the ones declared as DataAttributes in the target SDMX data structure definition.
  The mapping table is the following:
@@ -353,86 +353,90 @@
  |(% style="width:344px" %)Other Measures|(% style="width:341px" %)DataAttribute
  |(% style="width:344px" %)Attribute|(% style="width:341px" %)DataAttribute
--Even in this case, the resulting [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] definitions must be compliant with the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] consistency rules. For example, the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[DSD>>doc:xwiki:Glossary.Data structure definition.WebHome]] must have the attributeRelationship for the DataAttributes, which does not exist in [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]].
++Even in this case, the resulting SDMX definitions must be compliant with the SDMX consistency rules. For example, the SDMX DSD must have the attributeRelationship for the DataAttributes, which does not exist in VTL.
  === 12.3.5 Declaration of the mapping methods between data structures ===
--In order to define and understand properly [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] Transformations, the applied mapping methods must be specified in the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[structural metadata>>doc:xwiki:Glossary.Structural metadata.WebHome]]. If the default mapping method (Basic) is applied, no specification is needed.
++In order to define and understand properly VTL Transformations, the applied mapping methods must be specified in the SDMX structural metadata. If the default mapping method (Basic) is applied, no specification is needed.
--A customized mapping can be defined through the VtlMappingScheme and VtlDataflowMapping classes (see the section of the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] IM relevant to the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]]). A VtlDataflowMapping allows specifying the mapping methods to be used for a specific [[dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]], both in the direction from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] (toVtlMappingMethod) and from [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] (fromVtlMappingMethod); in fact a VtlDataflowMapping associates the structured URN that identifies a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] to its [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] alias and its mapping methods.
++A customized mapping can be defined through the VtlMappingScheme and VtlDataflowMapping classes (see the section of the SDMX IM relevant to the VTL). A VtlDataflowMapping allows specifying the mapping methods to be used for a specific dataflow, both in the direction from SDMX to VTL (toVtlMappingMethod) and from VTL to SDMX (fromVtlMappingMethod); in fact a VtlDataflowMapping associates the structured URN that identifies a SDMX Dataflow to its VTL alias and its mapping methods.
--It is possible to specify the toVtlMappingMethod and fromVtlMappingMethod also for the conventional [[dataflow>>doc:xwiki: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:xwiki:Glossary.Dataflow.WebHome]] are intended to override the default ones for such a [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]].
++It is possible to specify the toVtlMappingMethod and fromVtlMappingMethod also for the conventional dataflow called "generic_dataflow": in this case the specified mapping methods are intended to become the default ones, overriding the "Basic" methods. In turn, the toVtlMappingMethod and fromVtlMappingMethod declared for a specific Dataflow are intended to override the default ones for such a Dataflow.
--The VtlMappingScheme is a container for zero or more VtlDataflowMapping (it may contain also mappings towards [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] other than [[dataflows>>doc:xwiki:Glossary.Dataflow.WebHome]]).
++The VtlMappingScheme is a container for zero or more VtlDataflowMapping (it may contain also mappings towards artefacts other than dataflows).
  === 12.3.6 Mapping dataflow subsets to distinct VTL Data Sets ===
--Until now it has been assumed to (% style="color:#2ecc71" %)map(%%) one SMDX [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] to one [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:xwiki:Glossary.Data set.WebHome]] and vice-versa. This mapping one-to-one is not mandatory according to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] because a [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:xwiki: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:xwiki:Glossary.Representation.WebHome]] or storage (see [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] 2.0 User Manual page 24), therefore a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] can be seen either as a unique set of data observations (corresponding to one [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:xwiki:Glossary.Data set.WebHome]]) or as the union of many sets of data observations (each one corresponding to a distinct [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:xwiki:Glossary.Data set.WebHome]]).
++Until now it has been assumed to map one SMDX Dataflow to one VTL Data Set and vice-versa. This mapping one-to-one is not mandatory according to VTL because a VTL Data Set is meant to be a set of observations (data points) on a logical plane, having the same logical data structure and the same general meaning, independently of the possible physical representation or storage (see VTL 2.0 User Manual page 24), therefore a SDMX Dataflow can be seen either as a unique set of data observations (corresponding to one VTL Data Set) or as the union of many sets of data observations (each one corresponding to a distinct VTL Data Set).
--As a matter of fact, in some cases it can be useful to define [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] operations involving definite parts of a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] instead than the whole.{{footnote}}A typical example of this kind is the validation, and more in general the manipulation, of individual time series belonging to the same Dataflow, identifiable through the DimensionComponents of the Dataflow except the TimeDimension. The coding of these kind of operations might be simplified by mapping distinct time series (i.e. different parts of a SDMX Dataflow) to distinct VTL Data Sets.{{/footnote}}
++As a matter of fact, in some cases it can be useful to define VTL operations involving definite parts of a SDMX Dataflow instead than the whole.{{footnote}}A typical example of this kind is the validation, and more in general the manipulation, of individual time series belonging to the same Dataflow, identifiable through the DimensionComponents of the Dataflow except the TimeDimension. The coding of these kind of operations might be simplified by mapping distinct time series (i.e. different parts of a SDMX Dataflow) to distinct VTL Data Sets.{{/footnote}}
--Therefore, in order to make the coding of [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] operations simpler when applied on parts of [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflows>>doc:xwiki:Glossary.Dataflow.WebHome]], it is allowed to (% style="color:#2ecc71" %)map(%%) distinct parts of a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] to distinct [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:xwiki:Glossary.Data set.WebHome]] according to the following rules and conventions. This kind of mapping is possible both from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] and from [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]], as better explained below.{{footnote}}Please note that this kind of mapping is only an option at disposal of the definer of VTL Transformations; in fact it remains always possible to manipulate the needed parts of SDMX Dataflows by means of VTL operators (e.g. “sub”, “filter”, “calc”, “union” …), maintaining a mapping one-to-one between SDMX Dataflows and VTL Data Sets.{{/footnote}}
++Therefore, in order to make the coding of VTL operations simpler when applied on parts of SDMX Dataflows, it is allowed to map distinct parts of a SDMX Dataflow to distinct VTL Data Sets according to the following rules and conventions. This kind of mapping is possible both from SDMX to VTL and from VTL to SDMX, as better explained below.{{footnote}}Please note that this kind of mapping is only an option at disposal of the definer of VTL Transformations; in fact it remains always possible to manipulate the needed parts of SDMX Dataflows by means of VTL operators (e.g. “sub”, “filter”, “calc”, “union” …), maintaining a mapping one-to-one between SDMX Dataflows and VTL Data Sets.{{/footnote}}
--Given a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] and some predefined [[Dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] of its DataStructure, it is allowed to (% style="color:#2ecc71" %)map(%%) the subsets of observations that have the same combination of values for such [[Dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] to correspondent [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:xwiki:Glossary.Data set.WebHome]].
++Given a SDMX Dataflow and some predefined Dimensions of its DataStructure, it is allowed to map the subsets of observations that have the same combination of values for such Dimensions to correspondent VTL datasets.
--For example, assuming that the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] DF1(1.0.0) has the [[Dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] INDICATOR, TIME_PERIOD and COUNTRY, and that the user declares the [[Dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY as basis for the mapping (i.e. the mapping [[dimensions>>doc:xwiki:Glossary.Dimension.WebHome]]): the observations that have the same values for INDICATOR and COUNTRY would be (% style="color:#2ecc71" %)mapped(%%) to the same [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:xwiki:Glossary.Data set.WebHome]] (and vice-versa). In practice, this kind mapping is obtained like follows:
++For example, assuming that the SDMX Dataflow DF1(1.0.0) has the Dimensions INDICATOR, TIME_PERIOD and COUNTRY, and that the user declares the Dimensions INDICATOR and COUNTRY as basis for the mapping (i.e. the mapping dimensions): the observations that have the same values for INDICATOR and COUNTRY would be mapped to the same VTL dataset (and vice-versa). In practice, this kind mapping is obtained like follows:
--* For a given [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]], the user ([[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] definer) declares the DimensionComponents on which the mapping will be based, in a given order.{{footnote}}This definition is made through the ToVtlSubspace and ToVtlSpaceKey classes and/or the FromVtlSuperspace and FromVtlSpaceKey classes, depending on the direction of the mapping (“key” means “dimension”). The mapping of Dataflow subsets can be applied independently in the two directions, also according to different Dimensions. When no Dimension is declared for a given direction, it is assumed that the option of mapping different parts of a SDMX Dataflow to different VTL Data Sets is not used.{{/footnote}} Following the example above, imagine that the user declares the [[Dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY.
--* The [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:xwiki:Glossary.Data set.WebHome]] is given a name using a special notation also called “ordered concatenation” and composed of the following parts:
--** The reference to the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] (expressed according to the rules described in the previous paragraphs, i.e. URN, abbreviated URN or another alias); for example DF(1.0.0);
++* For a given SDMX Dataflow, the user (VTL definer) declares the DimensionComponents on which the mapping will be based, in a given order.{{footnote}}This definition is made through the ToVtlSubspace and ToVtlSpaceKey classes and/or the FromVtlSuperspace and FromVtlSpaceKey classes, depending on the direction of the mapping (“key” means “dimension”). The mapping of Dataflow subsets can be applied independently in the two directions, also according to different Dimensions. When no Dimension is declared for a given direction, it is assumed that the option of mapping different parts of a SDMX Dataflow to different VTL Data Sets is not used.{{/footnote}} Following the example above, imagine that the user declares the Dimensions INDICATOR and COUNTRY.
++* The VTL Data Set is given a name using a special notation also called “ordered concatenation” and composed of the following parts:
++** The reference to the SDMX Dataflow (expressed according to the rules described in the previous paragraphs, i.e. URN, abbreviated URN or another alias); for example DF(1.0.0);
  ** a slash (“/”) as a separator;{{footnote}}As a consequence of this formalism, a slash in the name of the VTL Data Set assumes the specific meaning of separator between the name of the Dataflow and the values of some of its Dimensions.{{/footnote}}
--The reference to a specific part of the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] above, expressed as the concatenation of the values that the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponents declared above must have, separated by dots (“.”) and written in the order in which these DimensionComponents are defined{{footnote}}This is the order in which the dimensions are defined in the ToVtlSpaceKey class or in the FromVtlSpaceKey class, depending on the direction of the mapping.{{/footnote}}. For example POPULATION.USA would mean that such a [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:xwiki:Glossary.Data set.WebHome]] is (% style="color:#2ecc71" %)mapped(%%) to the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] observations for which the [[dimension>>doc:xwiki:Glossary.Dimension.WebHome]] //INDICATOR// is equal to POPULATION and the [[dimension>>doc:xwiki:Glossary.Dimension.WebHome]] //COUNTRY// is equal to USA.
++The reference to a specific part of the SDMX Dataflow above, expressed as the concatenation of the values that the SDMX DimensionComponents declared above must have, separated by dots (“.”) and written in the order in which these DimensionComponents are defined{{footnote}}This is the order in which the dimensions are defined in the ToVtlSpaceKey class or in the FromVtlSpaceKey class, depending on the direction of the mapping.{{/footnote}}. For example POPULATION.USA would mean that such a VTL Data Set is mapped to the SDMX observations for which the dimension //INDICATOR// is equal to POPULATION and the dimension //COUNTRY// is equal to USA.
--In the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] Transformations, this kind of [[dataset>>doc:xwiki:Glossary.Data set.WebHome]] name must be referenced between single quotes because the slash (“/”) is not a regular character according to the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] rules.
++In the VTL Transformations, this kind of dataset name must be referenced between single quotes because the slash (“/”) is not a regular character according to the VTL rules.
--Therefore, the generic name of this kind of [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:xwiki:Glossary.Data set.WebHome]] would be:
++Therefore, the generic name of this kind of VTL datasets would be:
  'DF(1.0.0)/INDICATORvalue.COUNTRYvalue'
--Where DF(1.0.0) is the [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] and //INDICATORvalue// and //COUNTRYvalue //are placeholders for one value of the INDICATOR and COUNTRY [[dimensions>>doc:xwiki:Glossary.Dimension.WebHome]]. Instead the specific name of one of these [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:xwiki:Glossary.Data set.WebHome]] would be:
++Where DF(1.0.0) is the Dataflow and //INDICATORvalue// and //COUNTRYvalue //are placeholders for one value of the INDICATOR and COUNTRY dimensions. Instead the specific name of one of these VTL datasets would be:
  ‘DF(1.0.0)/POPULATION.USA’
--In particular, this is the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:xwiki:Glossary.Data set.WebHome]] that contains all the observations of the [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] DF(1.0.0) for which //INDICATOR// = POPULATION and //COUNTRY// = USA.
++In particular, this is the VTL dataset that contains all the observations of the Dataflow DF(1.0.0) for which //INDICATOR// = POPULATION and //COUNTRY// = USA.
--Let us now analyse the different meaning of this kind of mapping in the two mapping directions, i.e. from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] and from [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]].
++Let us now analyse the different meaning of this kind of mapping in the two mapping directions, i.e. from SDMX to VTL and from VTL to SDMX.
--As already said, the mapping from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] happens when the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[dataflows>>doc:xwiki:Glossary.Dataflow.WebHome]] are operand of [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] Transformations, instead the mapping from [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] happens when the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:xwiki:Glossary.Data set.WebHome]] that is result of Transformations{{footnote}}It should be remembered that, according to the VTL consistency rules, a given VTL dataset cannot be the result of more than one VTL Transformation.{{/footnote}} need to be treated as [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] objects. This kind of mapping can be applied independently in the two directions and the [[Dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] on which the mapping is based can be different in the two directions: these [[Dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] are defined in the ToVtlSpaceKey and in the FromVtlSpaceKey classes respectively.
++As already said, the mapping from SDMX to VTL happens when the SDMX dataflows are operand of VTL Transformations, instead the mapping from VTL to SDMX happens when the VTL Data Sets that is result of Transformations{{footnote}}It should be remembered that, according to the VTL consistency rules, a given VTL dataset cannot be the result of more than one VTL Transformation.{{/footnote}} need to be treated as SDMX objects. This kind of mapping can be applied independently in the two directions and the Dimensions on which the mapping is based can be different in the two directions: these Dimensions are defined in the ToVtlSpaceKey and in the FromVtlSpaceKey classes respectively.
--First, let us see what happens in the __mapping direction from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]]__, i.e. when parts of a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] (e.g. DF1(1.0.0)) need to be (% style="color:#2ecc71" %)mapped(%%) to distinct [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:xwiki:Glossary.Data set.WebHome]] that are operand of some [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] Transformations.
++First, let us see what happens in the __mapping direction from SDMX to VTL__, i.e. when parts of a SDMX Dataflow (e.g. DF1(1.0.0)) need to be mapped to distinct VTL Data Sets that are operand of some VTL Transformations.
--As already said, each [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Set>>doc:xwiki:Glossary.Data set.WebHome]] is assumed to contain all the observations of the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] having INDICATOR=//INDICATORvalue //and COUNTRY=// COUNTRYvalue//. For example, the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:xwiki:Glossary.Data set.WebHome]] ‘DF1(1.0.0)/POPULATION.USA’ would contain all the observations of DF1(1.0.0) having INDICATOR = POPULATION and COUNTRY = USA.
++As already said, each VTL Data Set is assumed to contain all the observations of the
--In order to obtain the data structure of these [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:xwiki:Glossary.Data set.WebHome]] from the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] one, it is assumed that the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] DimensionComponents on which the mapping is based are dropped, i.e. not maintained in the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] data structure; this is possible because their values are fixed for each one of the invoked [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:xwiki:Glossary.Data set.WebHome]]{{footnote}}If these DimensionComponents would not be dropped, the various VTL Data Sets resulting from this kind of mapping would have non-matching values for the Identifiers corresponding to the mapping Dimensions (e.g. POPULATION and COUNTRY). As a consequence, taking into account that the typical binary VTL operations at dataset level (+, -, *, / and so on) are executed on the observations having matching values for the identifiers, it would not be possible to compose the resulting VTL datasets one another (e.g. it would not be possible to calculate the population ratio between USA and CANADA).{{/footnote}}. After that, the mapping method from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] specified for the [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] DF1(1.0.0) is applied (i.e. basic, pivot …).
++SDMX Dataflow having INDICATOR=//INDICATORvalue //and COUNTRY=// COUNTRYvalue//. For example, the VTL dataset ‘DF1(1.0.0)/POPULATION.USA’ would contain all the observations of DF1(1.0.0) having INDICATOR = POPULATION and COUNTRY = USA.
--In the example above, for all the [[datasets>>doc:xwiki:Glossary.Data set.WebHome]] of the kind ‘DF1(1.0.0)///INDICATORvalue//.//COUNTRYvalue//’, the [[dimensions>>doc:xwiki:Glossary.Dimension.WebHome]] INDICATOR and COUNTRY would be dropped so that the data structure of all the resulting [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:xwiki:Glossary.Data set.WebHome]] would have the identifier TIME_PERIOD only.
++In order to obtain the data structure of these VTL Data Sets from the SDMX one, it is assumed that the SDMX DimensionComponents on which the mapping is based are dropped, i.e. not maintained in the VTL data structure; this is possible because their values are fixed for each one of the invoked VTL Data Sets{{footnote}}If these DimensionComponents would not be dropped, the various VTL Data Sets resulting from this kind of mapping would have non-matching values for the Identifiers corresponding to the mapping Dimensions (e.g. POPULATION and COUNTRY). As a consequence, taking into account that the typical binary VTL operations at dataset level (+, -, *, / and so on) are executed on the observations having matching values for the identifiers, it would not be possible to compose the resulting VTL datasets one another (e.g. it would not be possible to calculate the population ratio between USA and CANADA).{{/footnote}}. After that, the mapping method from SDMX to VTL specified for the Dataflow DF1(1.0.0) is applied (i.e. basic, pivot …).
--It should be noted that the desired [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:xwiki:Glossary.Data set.WebHome]] (i.e. of the kind ‘DF1(1.0.0)/// INDICATORvalue//.//COUNTRYvalue//’) can be obtained also by applying the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] operator “**sub**” (subspace) to the [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] DF1(1.0.0), like in the following [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] expression:
++In the example above, for all the datasets of the kind ‘DF1(1.0.0)///INDICATORvalue//.//COUNTRYvalue//’, the dimensions INDICATOR and COUNTRY would be dropped so that the data structure of all the resulting VTL Data Sets would have the identifier TIME_PERIOD only.
++It should be noted that the desired VTL Data Sets (i.e. of the kind ‘DF1(1.0.0)/// INDICATORvalue//.//COUNTRYvalue//’) can be obtained also by applying the VTL operator “**sub**” (subspace) to the Dataflow DF1(1.0.0), like in the following VTL expression:
++
  [[image:1747388275998-621.png]]
--In fact the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] operator “sub” has exactly the same behaviour. Therefore, (% style="color:#2ecc71" %)mapping(%%) different parts of a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] to different [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[Data Sets>>doc:xwiki:Glossary.Data set.WebHome]] in the direction from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki: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:xwiki:Glossary.Dataflow.WebHome]].{{footnote}}In case the ordered concatenation notation is used, the VTL Transformation described above, e.g. ‘DF1(1.0)/POPULATION.USA’ := DF1(1.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“USA”], is implicitly executed. In order to test the overall compliance of the VTL program to the VTL consistency rules, it has to be considered as part of the VTL program even if it is not explicitly coded.{{/footnote}}
++In fact the VTL operator “sub” has exactly the same behaviour. Therefore, mapping different parts of a SDMX Dataflow to different VTL Data Sets in the direction from SDMX to VTL through the ordered concatenation notation is equivalent to a proper use of the operator “**sub**” on such a Dataflow.{{footnote}}In case the ordered concatenation notation is used, the VTL Transformation described above, e.g. ‘DF1(1.0)/POPULATION.USA’ := DF1(1.0) [ sub INDICATOR=“POPULATION”, COUNTRY=“USA”], is implicitly executed. In order to test the overall compliance of the VTL program to the VTL consistency rules, it has to be considered as part of the VTL program even if it is not explicitly coded.{{/footnote}}
--In the direction from [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] to [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] it is allowed to omit the value of one or more DimensionComponents on which the (% style="color:#2ecc71" %)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:xwiki:Glossary.Dimension.WebHome]] all the values are kept and the [[Dimension>>doc:xwiki:Glossary.Dimension.WebHome]] is not dropped.
++In the direction from SDMX to VTL it is allowed to omit the value of one or more
--For example, ‘DF(1.0.0)/POPULATION.’ (note the dot in the end of the name) is the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[dataset>>doc:xwiki:Glossary.Data set.WebHome]] that contains all the observations of the [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] DF(1.0.0) for which //INDICATOR// = POPULATION and COUNTRY = any value.
++DimensionComponents on which the mapping is based, but maintaining all the separating dots (therefore it may happen to find two or more consecutive dots and dots in the beginning or in the end). The absence of value means that for the corresponding Dimension all the values are kept and the Dimension is not dropped.
--This is equivalent to the application of the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] “sub” operator only to the identifier //INDICATOR//:
++For example, ‘DF(1.0.0)/POPULATION.’ (note the dot in the end of the name) is the VTL dataset that contains all the observations of the Dataflow DF(1.0.0) for which //INDICATOR// = POPULATION and COUNTRY = any value.
++This is equivalent to the application of the VTL “sub” operator only to the identifier //INDICATOR//:
++
  [[image:1747388244829-693.png]]
  Therefore the VTL Data Set ‘DF1(1.0.0)/POPULATION.’ would have the identifiers COUNTRY and TIME_PERIOD.
--Heterogeneous invocations of the same [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] are allowed, i.e. omitting different
++Heterogeneous invocations of the same Dataflow are allowed, i.e. omitting different
  Dimensions in different invocations.
--Let us now analyse __the mapping direction from [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] to [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]]__.
++Let us now analyse __the mapping direction from VTL to SDMX__.
--In this situation, distinct parts of a [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[Dataflow>>doc:xwiki:Glossary.Dataflow.WebHome]] are calculated as distinct [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] [[datasets>>doc:xwiki:Glossary.Data set.WebHome]], under the (% style="color:#2ecc71" %)constraint(%%) that they must have the same [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] data structure.
++In this situation, distinct parts of a SDMX Dataflow are calculated as distinct VTL datasets, under the constraint that they must have the same VTL data structure.
--For example, let us assume that the [[VTL>>doc:xwiki:Glossary.Validation and transformation language.WebHome]] programmer wants to calculate the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]]
++For example, let us assume that the VTL programmer wants to calculate the SDMX
  Dataflow DF2(1.0.0) having the Dimensions TIME_PERIOD, INDICATOR, and COUNTRY and that such a programmer finds it convenient to calculate separately the parts of DF2(1.0.0) that have different combinations of values for INDICATOR and COUNTRY: