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... ... @@ -2,9 +2,10 @@
2 2  {{toc/}}
3 3  {{/box}}
4 4  
5 -== 12.1 Introduction ==
5 +1.
6 +11. Introduction
6 6  
7 -The Validation and Transformation Language (VTL) supports the definition of Transformations, which are algorithms to calculate new data starting from already existing ones{{footnote}}The Validation and Transformation Language is a standard language designed and published under the SDMX initiative. VTL is described in the VTL User and Reference Guides available on the SDMX website https://sdmx.org.{{/footnote}}. The purpose of the VTL in the SDMX context is to enable the:
8 +The Validation and Transformation Language (VTL) supports the definition of Transformations, which are algorithms to calculate new data starting from already existing ones[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[1~]^^>>path:#_ftn1]](%%). The purpose of the VTL in the SDMX context is to enable the:
8 8  
9 9  * definition of validation and transformation algorithms, in order to specify how to calculate new data from existing ones;
10 10  * exchange of the definition of VTL algorithms, also together the definition of the data structures of the involved data (for example, exchange the data structures of a reporting framework together with the validation rules to be applied, exchange the input and output data structures of a calculation task together with the VTL Transformations describing the calculation algorithms);
... ... @@ -12,31 +12,33 @@
12 12  
13 13  It is important to note that the VTL has its own information model (IM), derived from the Generic Statistical Information Model (GSIM) and described in the VTL User Guide. The VTL IM is designed to be compatible with more standards, like SDMX, DDI (Data Documentation Initiative) and GSIM, and includes the model artefacts that can be manipulated (inputs and/or outputs of Transformations, e.g. "Data Set", "Data Structure") and the model artefacts that allow the definition of the transformation algorithms (e.g. "Transformation", "Transformation Scheme").
14 14  
15 -The VTL language can be applied to SDMX artefacts by mapping the SDMX IM model artefacts to the model artefacts that VTL can manipulate{{footnote}}In this chapter, in order to distinguish VTL and SDMX model artefacts, the VTL ones are written in the Arial font while the SDMX ones in Courier New.{{/footnote}}. Thus, the SDMX artefacts can be used in VTL as inputs and/or outputs of Transformations. It is important to be aware that the artefacts do not always have the same names in the SDMX and VTL IMs, nor do they always have the same meaning. The more evident example is given by the SDMX Dataset and the VTL "Data Set", which do not correspond one another: as a matter of fact, the VTL "Data Set" maps to the SDMX "Dataflow", while the SDMX "Dataset" has no explicit mapping to VTL (such an abstraction is not needed in the definition of VTL Transformations). A SDMX "Dataset", however, is an instance of a SDMX "Dataflow" and can be the artefact on which the VTL transformations are executed (i.e., the Transformations are defined on Dataflows and are applied to Dataflow instances that can be Datasets).
16 +The VTL language can be applied to SDMX artefacts by mapping the SDMX IM model artefacts to the model artefacts that VTL can manipulate[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[2~]^^>>path:#_ftn2]](%%). Thus, the SDMX artefacts can be used in VTL as inputs and/or outputs of Transformations. It is important to be aware that the artefacts do not always have the same names in the SDMX and VTL IMs, nor do they always have the same meaning. The more evident example is given by the SDMX Dataset and the VTL "Data Set", which do not correspond one another: as a matter of fact, the VTL "Data Set" maps to the SDMX "Dataflow", while the SDMX "Dataset" has no explicit mapping to VTL (such an abstraction is not needed in the definition of VTL Transformations). A SDMX "Dataset", however, is an instance of a SDMX "Dataflow" and can be the artefact on which the VTL transformations are executed (i.e., the Transformations are defined on Dataflows and are applied to Dataflow instances that can be Datasets).
16 16  
17 17  The VTL programs (Transformation Schemes) are represented in SDMX through the TransformationScheme maintainable class which is composed of Transformation (nameable artefact). Each Transformation assigns the outcome of the evaluation of a VTL expression to a result.
18 18  
19 19  This section does not explain the VTL language or any of the content published in the VTL guides. Rather, this is a description of how the VTL can be used in the SDMX context and applied to SDMX artefacts.
20 20  
21 -== 12.2 References to SDMX artefacts from VTL statements ==
22 +1.
23 +11. References to SDMX artefacts from VTL statements
24 +111. Introduction
22 22  
23 -=== 12.2.1 Introduction ===
24 -
25 25  The VTL can manipulate SDMX artefacts (or objects) by referencing them through predefined conventional names (aliases).
26 26  
27 27  The alias of an SDMX artefact can be its URN (Universal Resource Name), an abbreviation of its URN or another user-defined name.
28 28  
29 -In any case, the aliases used in the VTL Transformations have to be mapped to the SDMX artefacts through the VtlMappingScheme and VtlMapping classes (see the section of the SDMX IM relevant to the VTL). A VtlMapping allows specifying the aliases to be used in the VTL Transformations, Rulesets{{footnote}}See also the section "VTL-DL Rulesets" in the VTL Reference Manual.{{/footnote}} or User Defined Operators{{footnote}}The VTLMappings are used also for User Defined Operators (UDO). Although UDOs are envisaged to be defined on generic operands, so that the specific artefacts to be manipulated are passed as parameters at their invocation, it is also possible that an UDO invokes directly some specific SDMX artefacts. These SDMX artefacts have to be mapped to the corresponding aliases used in the definition of the UDO through the VtlMappingScheme and VtlMapping classes as well.{{/footnote}} to reference SDMX artefacts. A VtlMappingScheme is a container for zero or more VtlMapping.
30 +In any case, the aliases used in the VTL Transformations have to be mapped to the SDMX artefacts through the VtlMappingScheme and VtlMapping classes (see the section of the SDMX IM relevant to the VTL). A VtlMapping allows specifying the aliases to be used in the VTL Transformations, Rulesets[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[3~]^^>>path:#_ftn3]](%%) or User Defined Operators[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[4~]^^>>path:#_ftn4]](%%) to reference SDMX artefacts. A VtlMappingScheme is a container for zero or more VtlMapping.
30 30  
31 31  The correspondence between an alias and a SDMX artefact must be one-to-one, meaning that a generic alias identifies one and just one SDMX artefact while a SDMX artefact is identified by one and just one alias. In other words, within a VtlMappingScheme an artefact can have just one alias and different artefacts cannot have the same alias.
32 32  
33 33  The references through the URN and the abbreviated URN are described in the following paragraphs.
34 34  
35 -=== 12.2.2 References through the URN ===
36 +1.
37 +11.
38 +111. References through the URN
36 36  
37 37  This approach has the advantage that in the VTL code the URN of the referenced artefacts is directly intelligible by a human reader but has the drawback that the references are verbose.
38 38  
39 -The SDMX URN{{footnote}}For a complete description of the structure of the URN see the SDMX 2.1 Standards - Section 5 - Registry Specifications, paragraph 6.2.2 ("Universal Resource Name (URN)").{{/footnote}}(% style="font-size:12px" %) (%%)is the concatenation of the following parts, separated by special symbols like dot, equal, asterisk, comma, and parenthesis:
42 +The SDMX URN[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[5~]^^>>path:#_ftn5]](%%) is the concatenation of the following parts, separated by special symbols like dot, equal, asterisk, comma, and parenthesis:
40 40  
41 41  * SDMXprefix
42 42  * SDMX-IM-package-name
... ... @@ -44,13 +44,15 @@
44 44  * agency-id
45 45  * maintainedobject-id
46 46  * maintainedobject-version
47 -* container-object-id{{footnote}}The container-object-id can repeat and may not be present.{{/footnote}}
50 +* container-object-id [[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[6~]^^>>path:#_ftn6]]
48 48  * object-id
49 49  
50 50  The generic structure of the URN is the following:
51 51  
52 -SDMXprefix.SDMX-IM-package-name.class-name=agency-id:maintainedobject-id (maintainedobject-version).*container-object-id.object-id
55 +SDMXprefix.SDMX-IM-package-name.class-name=agency-id:maintainedobject-id
53 53  
57 +(maintainedobject-version).*container-object-id.object-id
58 +
54 54  The **SDMXprefix** is "urn:sdmx:org", always the same for all SDMX artefacts.
55 55  
56 56  The SDMX-IM-package-name** **is the concatenation of the string** **"sdmx.infomodel." with the package-name, which the artefact belongs to. For example, for referencing a Dataflow the SDMX-IM-package-name is "sdmx.infomodel.datastructure", because the class Dataflow belongs to the package "datastructure".
... ... @@ -59,7 +59,7 @@
59 59  
60 60  The agency-id is the acronym of the agency that owns the definition of the artefact, for example for the Eurostat artefacts the agency-id is "ESTAT"). The agency-id can be composite (for example AgencyA.Dept1.Unit2).
61 61  
62 -The maintainedobject-id is the name of the maintained object which the artefact belongs to, and in case the artefact itself is maintainable{{footnote}}i.e., the artefact belongs to a maintainable class{{/footnote}}, coincides with the name of the artefact. Therefore the maintainedobject-id depends on the class of the artefact:
67 +The maintainedobject-id is the name of the maintained object which the artefact belongs to, and in case the artefact itself is maintainable[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[7~]^^>>path:#_ftn7]](%%), coincides with the name of the artefact. Therefore the maintainedobject-id depends on the class of the artefact:
63 63  
64 64  * if the artefact is a Dataflow, which is a maintainable class, the maintainedobject-id is the Dataflow name (dataflow-id);
65 65  * if the artefact is a Dimension, Measure, TimeDimension or DataAttribute, which are not maintainable and belong to the
... ... @@ -71,21 +71,28 @@
71 71  
72 72  The maintainedobject-version is the version, according to the SDMX versioning rules, of the maintained object which the artefact belongs to (for example, possible versions might be 1.0, 2.3, 1.0.0, 2.1.0 or 3.1.2).
73 73  
74 -The container-object-id does not apply to the classes that can be referenced in VTL Transformations, therefore is not present in their URN.
79 +The container-object-id does not apply to the classes that can be referenced in VTL Transformations, therefore is not present in their URN
75 75  
76 76  The object-id is the name of the non-maintainable artefact (when the artefact is maintainable its name is already specified as the maintainedobject-id, see above), in particular it has to be specified:
77 77  
78 -* if the artefact is a Dimension, TimeDimension, Measure or DataAttribute (the object-id is the name of one of the artefacts above, which are data structure components)
83 +* if the artefact is a Dimension, TimeDimension, Measure or
84 +
85 +DataAttribute (the object-id is the name of one of the artefacts above, which are data structure components)
86 +
79 79  * if the artefact is a Concept (the object-id is the name of the Concept)
80 80  
81 -For example, by using the URN, the VTL Transformation that sums two SDMX Dataflows DF1 and DF2 and assigns the result to a third persistent Dataflow DFR, assuming that DF1, DF2 and DFR are the maintainedobject-id of the three Dataflows, that their version is 1.0.0 and their Agency is AG, would be written as{{footnote}}Since these references to SDMX objects include non-permitted characters as per the VTL ID notation, they need to be included between single quotes, according to the VTL rules for irregular names.{{/footnote}}:
89 +For example, by using the URN, the VTL Transformation that sums two SDMX Dataflows DF1 and DF2 and assigns the result to a third persistent Dataflow DFR, assuming that DF1, DF2 and DFR are the maintainedobject-id of the three Dataflows, that their version is 1.0.0 and their Agency is AG, would be written as[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[8~]^^>>path:#_ftn8]](%%):
82 82  
83 ->(% style="font-size:16px" %) 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' <-
84 ->(% style="font-size:16px" %) 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
85 ->(% style="font-size:16px" %) 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
91 +'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' <-
86 86  
87 -=== 12.2.3 Abbreviation of the URN ===
93 +'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
88 88  
95 +'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
96 +
97 +1.
98 +11.
99 +111. Abbreviation of the URN
100 +
89 89  The complete formulation of the URN described above is exhaustive but verbose, even for very simple statements. In order to reduce the verbosity through a simplified identifier and make the work of transformation definers easier, proper abbreviations of the URN are possible. Using this approach, the referenced artefacts remain intelligible in the VTL code by a human reader.
90 90  
91 91  The URN can be abbreviated by omitting the parts that are not essential for the identification of the artefact or that can be deduced from other available information, including the context in which the invocation is made. The possible abbreviations are described below.
... ... @@ -93,10 +93,14 @@
93 93  * The SDMXprefix can be omitted for all the SDMX objects, because it is a prefixed string (urn:sdmx:org), always the same for SDMX objects.
94 94  * The SDMX-IM-package-name** **can be omitted as well because it can be deduced from the class-name that follows it (the table of the SDMX-IM packages and classes that allows this deduction is in the SDMX 2.1 Standards - Section 5 - Registry Specifications, paragraph 6.2.3). In particular, considering the object classes of the artefacts that VTL can reference, the package is:
95 95  ** "datastructure" for the classes Dataflow, Dimension, TimeDimension, Measure, DataAttribute, o "conceptscheme" for the class Concept, o "codelist" for the class Codelist.
96 -* The class-name can be omitted as it can be deduced from the VTL invocation. In particular, starting from the VTL class of the invoked artefact (e.g. dataset, component, identifier, measure, attribute, variable, valuedomain), which is known given the syntax of the invoking VTL operator{{footnote}}For the syntax of the VTL operators see the VTL Reference Manual{{/footnote}}, the SDMX class can be deduced from the mapping rules between VTL and SDMX (see the section "Mapping between VTL and SDMX" hereinafter){{footnote}}In case the invoked artefact is a VTL component, which can be invoked only within the invocation of a VTL data set (SDMX Dataflow), the specific SDMX class-name (e.g. Dimension, TimeDimension, Measure or DataAttribute) can be deduced from the data structure of the SDMX Dataflow, which the component belongs to.{{/footnote}}.
97 -* If the agency-id is not specified, it is assumed by default equal to the agency-id of the TransformationScheme, UserDefinedOperatorScheme or RulesetScheme from which the artefact is invoked. For example, the agencyid can be omitted if it is the same as the invoking TransformationScheme and cannot be omitted if the artefact comes from another agency{{footnote}}If the Agency is composite (for example AgencyA.Dept1.Unit2), the agency is considered different even if only part of the composite name is different (for example AgencyA.Dept1.Unit3 is a different Agency than the previous one). Moreover the agency-id cannot be omitted in part (i.e., if a TransformationScheme owned by AgencyA.Dept1.Unit2 references an artefact coming from AgencyA.Dept1.Unit3, the specification of the agency-id becomes mandatory and must be complete, without omitting the possibly equal parts like AgencyA.Dept1){{/footnote}}. Take also into account that, according to the VTL consistency rules, the agency of the result of a Transformation must be the same as its TransformationScheme, therefore the agency-id can be omitted for all the results (left part of Transformation statements).
108 +* The class-name can be omitted as it can be deduced from the VTL invocation. In particular, starting from the VTL class of the invoked artefact (e.g. dataset, component, identifier, measure, attribute, variable, valuedomain), which is known given the syntax of the invoking VTL operator[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[9~]^^>>path:#_ftn9]](%%), the SDMX class can be deduced from the mapping rules between VTL and SDMX (see the section "Mapping between VTL and SDMX" hereinafter)[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[10~]^^>>path:#_ftn10]](%%).
109 +* If the agency-id is not specified, it is assumed by default equal to the agency-id of the TransformationScheme, UserDefinedOperatorScheme or RulesetScheme from which the artefact is invoked. For example, the agencyid can be omitted if it is the same as the invoking TransformationScheme and cannot be omitted if the artefact comes from another agency[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[11~]^^>>path:#_ftn11]](%%). Take also into account that, according to the VTL consistency rules, the agency of the result of a Transformation must be the same as its TransformationScheme, therefore the agency-id can be omitted for all the results (left part of Transformation statements).
98 98  * As for the maintainedobject-id, this is essential in some cases while in other cases it can be omitted: o if the referenced artefact is a Dataflow, which is a maintainable class, the maintainedobject-id is the dataflow-id and obviously cannot be omitted;
99 -** if the referenced artefact is a Dimension, TimeDimension, Measure, DataAttribute, which are not maintainable and belong to the DataStructure maintainable class, the maintainedobject-id is the dataStructure-id and can be omitted, given that these components are always invoked within the invocation of a Dataflow, whose dataStructure-id can be deduced from the SDMX structural definitions;
111 +** if the referenced artefact is a Dimension, TimeDimension, Measure,
112 +
113 +DataAttribute, which are not maintainable and belong to the DataStructure maintainable class, the maintainedobject-id is the dataStructure-id and can be omitted, given that these components are always invoked within the invocation of a Dataflow, whose dataStructure-id can be deduced from the SDMX structural definitions;
114 +
115 +*
100 100  ** if the referenced artefact is a Concept, which is not maintainable and belong to the ConceptScheme maintainable class, the maintained object is the conceptScheme-id and cannot be omitted;
101 101  ** if the referenced artefact is a Codelist, which is a maintainable class, the maintainedobject-id is the codelist-id and obviously cannot be omitted.
102 102  * When the maintainedobject-id is omitted, the maintainedobject-version is omitted too. When the maintainedobject-id is not omitted and the maintainedobject-version is omitted, the version 1.0 is assumed by default.
... ... @@ -117,7 +117,7 @@
117 117  
118 118  DFR := DF1 + DF2
119 119  
120 -The references to the Codelists can be simplified similarly. For example, given the non-abbreviated reference to the Codelist AG:CL_FREQ(1.0.0), which is{{footnote}}Single quotes are needed because this reference is not a VTL regular name. 19 Single quotes are not needed in this case because CL_FREQ is a VTL regular name.{{/footnote}}:
136 +The references to the Codelists can be simplified similarly. For example, given the non-abbreviated reference to the Codelist AG:CL_FREQ(1.0.0), which is[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[12~]^^>>path:#_ftn12]](%%):
121 121  
122 122  'urn:sdmx:org.sdmx.infomodel.codelist.Codelist=AG:CL_FREQ(1.0.0)'
123 123  
... ... @@ -135,7 +135,7 @@
135 135  
136 136  SECTOR
137 137  
138 -For example, the Transformation for renaming the component SECTOR of the Dataflow DF1 into SEC can be written as{{footnote}}The result DFR(1.0.0) is be equal to DF1(1.0.0) save that the component SECTOR is called SEC{{/footnote}}:
154 +For example, the Transformation for renaming the component SECTOR of the Dataflow DF1 into SEC can be written as[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[13~]^^>>path:#_ftn13]](%%):
139 139  
140 140  'DFR(1.0.0)' := 'DF1(1.0.0)' [rename SECTOR to SEC]
141 141  
... ... @@ -155,37 +155,43 @@
155 155  
156 156  The artefact (Component, Concept, Codelist …) which the Values are referred to can be deduced from the context in which the reference is made, taking also into account the VTL syntax. In the Transformation above, for example, the values 0 and 2500 are compared to the values of the measures of DF1(1.0.0).
157 157  
158 -=== 12.2.4 User-defined alias ===
174 +1.
175 +11.
176 +111. User-defined alias
159 159  
160 160  The third possibility for referencing SDMX artefacts from VTL statements is to use user-defined aliases not related to the SDMX URN of the artefact.
161 161  
162 162  This approach gives preference to the use of symbolic names for the SDMX artefacts. As a consequence, in the VTL code the referenced artefacts may become not directly intelligible by a human reader. In any case, the VTL aliases are associated to the SDMX URN through the VtlMappingScheme and VtlMapping classes. These classes provide for structured references to SDMX artefacts whatever kind of reference is used in VTL statements (URN, abbreviated URN or user-defined aliases).
163 163  
164 -=== 12.2.5 References to SDMX artefacts from VTL Rulesets ===
182 +1.
183 +11.
184 +111. References to SDMX artefacts from VTL Rulesets
165 165  
166 166  The VTL Rulesets allow defining sets of reusable Rules that can be applied by some VTL operators, like the ones for validation and hierarchical roll-up. A "Rule" consists in a relationship between Values belonging to some Value Domains or taken by some Variables, for example: (i) when the Country is USA then the Currency is USD; (ii) the Benelux is composed by Belgium, Luxembourg, Netherlands.
167 167  
168 168  The VTL Rulesets have a signature, in which the Value Domains or the Variables on which the Ruleset is defined are declared, and a body, which contains the Rules.
169 169  
170 -In the signature, given the mapping between VTL and SDMX better described in the following paragraphs, a reference to a VTL Value Domain becomes a reference to a SDMX Codelist, while a reference to a VTL Represented Variable becomes a reference to a SDMX Concept, assuming for it a definite representation{{footnote}}Rulesets of this kind cannot be reused when the referenced Concept has a different representation.{{/footnote}}.
190 +In the signature, given the mapping between VTL and SDMX better described in the following paragraphs, a reference to a VTL Value Domain becomes a reference to a SDMX Codelist, while a reference to a VTL Represented Variable becomes a reference to a SDMX Concept, assuming for it a definite representation[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[14~]^^>>path:#_ftn14]](%%).
171 171  
172 -In general, for referencing SDMX Codelists and Concepts, the conventions described in the previous paragraphs apply. In the Ruleset syntax, the elements that reference SDMX artefacts are called "valueDomain" and "variable" for the Datapoint Rulesets and "ruleValueDomain", "ruleVariable", "condValueDomain" "condVariable" for the Hierarchical Rulesets). The syntax of the Ruleset signature allows also to define aliases of the elements above, these aliases are valid only within the specific Ruleset definition statement and cannot be mapped to SDMX.{{footnote}}See also the section "VTL-DL Rulesets" in the VTL Reference Manual.{{/footnote}}
192 +In general, for referencing SDMX Codelists and Concepts, the conventions described in the previous paragraphs apply. In the Ruleset syntax, the elements that reference SDMX artefacts are called "valueDomain" and "variable" for the Datapoint Rulesets and "ruleValueDomain", "ruleVariable", "condValueDomain" "condVariable" for the Hierarchical Rulesets). The syntax of the Ruleset signature allows also to define aliases of the elements above, these aliases are valid only within the specific Ruleset definition statement and cannot be mapped to SDMX.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[15~]^^>>path:#_ftn15]]
173 173  
174 174  In the body of the Rulesets, the Codes and in general all the Values can be written without any other specification, because the artefact, which the Values are referred (Codelist, Concept) to can be deduced from the Ruleset signature.
175 175  
176 -== 12.3 Mapping between SDMX and VTL artefacts ==
196 +1.
197 +11. Mapping between SDMX and VTL artefacts
198 +111. When the mapping occurs
177 177  
178 -=== 12.3.1. When the mapping occurs ===
179 -
180 180  The mapping methods between the VTL and SDMX object classes allow transforming a SDMX definition in a VTL one and vice-versa for the artefacts to be manipulated. It should be remembered that VTL programs (i.e. Transformation Schemes) are represented in SDMX through the TransformationScheme maintainable class which is composed of Transformations (nameable artefacts). Each Transformation assigns the outcome of the evaluation of a VTL expression to a result: the input operands of the expression and the result can be SDMX artefacts. Every time a SDMX object is referenced in a VTL Transformation as an input operand, there is the need to generate a VTL definition of the object, so that the VTL operations can take place. This can be made starting from the SDMX definition and applying a SDMX-VTL mapping method in the direction from SDMX to VTL. The possible mapping methods from SDMX to VTL are described in the following paragraphs and are conceived to allow the automatic deduction of the VTL definition of the object from the knowledge of the SDMX definition.
181 181  
182 -In the opposite direction, every time an object calculated by means of VTL must be treated as a SDMX object (for example for exchanging it through SDMX), there is the need of a SDMX definition of the object, so that the SDMX operations can take place. The SDMX definition is needed for the VTL objects for which a SDMX use is envisaged{{footnote}}If a calculated artefact is persistent, it needs a persistent definition, i.e. a SDMX definition in a SDMX environment. In addition, possible calculated artefact that are not persistent may require a SDMX definition, for example when the result of a nonpersistent calculation is disseminated through SDMX tools (like an inquiry tool).{{/footnote}}.
202 +In the opposite direction, every time an object calculated by means of VTL must be treated as a SDMX object (for example for exchanging it through SDMX), there is the need of a SDMX definition of the object, so that the SDMX operations can take place. The SDMX definition is needed for the VTL objects for which a SDMX use is envisaged[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[16~]^^>>path:#_ftn16]](%%).
183 183  
184 184  The mapping methods from VTL to SDMX are described in the following paragraphs as well, however they do not allow the complete SDMX definition to be automatically deduced from the VTL definition, more than all because the former typically contains additional information in respect to the latter. For example, the definition of a SDMX DSD includes also some mandatory information not available in VTL (like the concept scheme to which the SDMX components refer, the ‘usage’ and ‘attributeRelationship’ for the DataAttributes and so on). Therefore the mapping methods from VTL to SDMX provide only a general guidance for generating SDMX definitions properly starting from the information available in VTL, independently of how the SDMX definition it is actually generated (manually, automatically or part and part).
185 185  
186 -=== 12.3.2 General mapping of VTL and SDMX data structures ===
206 +1.
207 +11.
208 +111. General mapping of VTL and SDMX data structures
187 187  
188 -This section makes reference to the VTL "Model for data and their structure"{{footnote}}See the VTL 2.0 User Manual{{/footnote}} and the correspondent SDMX "Data Structure Definition"{{footnote}}See the SDMX Standards Section 2 – Information Model{{/footnote}}.
210 +This section makes reference to the VTL "Model for data and their structure"[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[17~]^^>>path:#_ftn17]](%%) and the correspondent SDMX "Data Structure Definition"{{footnote}}See the SDMX Standards Section 2 – Information Model{{/footnote}}.
189 189  
190 190  The main type of artefact that the VTL can manipulate is the VTL Data Set, which in general is mapped to the SDMX Dataflow. This means that a VTL Transformation, in the SDMX context, expresses the algorithm for calculating a derived Dataflow starting from some already existing Dataflows (either collected or derived).{{footnote}}Besides the mapping between one SDMX Dataflow and one VTL Data Set, it is also possible to map distinct parts of a SDMX Dataflow to different VTL Data Set, as explained in a following paragraph.{{/footnote}}
191 191  
... ... @@ -199,9 +199,11 @@
199 199  
200 200  The possible mapping options are described in more detail in the following sections.
201 201  
202 -=== 12.3.2 Mapping from SDMX to VTL data structures ===
224 +1.
225 +11.
226 +111. Mapping from SDMX to VTL data structures
203 203  
204 -==== 12.3.3.1 Basic Mapping ====
228 +**12.3.3.1 Basic Mapping**
205 205  
206 206  The main mapping method from SDMX to VTL is called **Basic **mapping. This is considered as the default mapping method and is applied unless a different method is specified through the VtlMappingScheme and VtlDataflowMapping classes.
207 207  
... ... @@ -217,7 +217,7 @@
217 217  
218 218  With the Basic mapping, one SDMX observation^^27^^ generates one VTL data point.
219 219  
220 -==== 12.3.3.2 Pivot Mapping ====
244 +**12.3.3.2 Pivot Mapping**
221 221  
222 222  An alternative mapping method from SDMX to VTL is the **Pivot **mapping, which makes sense and is different from the Basic method only for the SDMX data structures that contain a Dimension that plays the role of measure dimension (like in SDMX 2.1) and just one Measure. Through this method, these structures can be mapped to multimeasure VTL data structures. Besides that, a user may choose to use any Dimension acting as a list of Measures (e.g., a Dimension with indicators), either by considering the “Measure” role of a Dimension, or at will using any coded Dimension. Of course, in SDMX 3.0, this can only work when only one Measure is defined in the DSD.
223 223  
... ... @@ -248,6 +248,7 @@
248 248  |DataAttribute not depending on the MeasureDimension|Attribute
249 249  |DataAttribute depending on the MeasureDimension|(((
250 250  One Attribute for each Code of the
275 +
251 251  SDMX MeasureDimension
252 252  )))
253 253  
... ... @@ -260,10 +260,13 @@
260 260  
261 261  Identifiers, (time) Identifier and Attributes.
262 262  
263 -* The value of the Measure of the SDMX observation belonging to the set above and having MeasureDimension=Cj becomes the value of the VTL Measure Cj
288 +* The value of the Measure of the SDMX observation belonging to the set above and having MeasureDimension=Cj becomes the value of the VTL Measure
289 +
290 +Cj
291 +
264 264  * For the SDMX DataAttributes depending on the MeasureDimension, the value of the DataAttribute DA of the SDMX observation belonging to the set above and having MeasureDimension=Cj becomes the value of the VTL Attribute DA_Cj
265 265  
266 -==== 12.3.3.3 From SDMX DataAttributes to VTL Measures ====
294 +**12.3.3.3 From SDMX DataAttributes to VTL Measures**
267 267  
268 268  * In some cases, it may happen that the DataAttributes of the SDMX DataStructure need to be managed as Measures in VTL. Therefore, a variant of both the methods above consists in transforming all the SDMX DataAttributes in VTL Measures. When DataAttributes are converted to Measures, the two methods above are called Basic_A2M and Pivot_A2M (the suffix "A2M" stands for Attributes to Measures). Obviously, the resulting VTL data structure is, in general, multi-measure and does not contain
269 269  
... ... @@ -273,9 +273,11 @@
273 273  
274 274  Proper VTL features allow changing the role of specific attributes even after the SDMX to VTL mapping: they can be useful when only some of the DataAttributes need to be managed as VTL Measures.
275 275  
276 -=== 12.3.4 Mapping from VTL to SDMX data structures ===
304 +1.
305 +11.
306 +111. Mapping from VTL to SDMX data structures
277 277  
278 -==== 12.3.4.1 Basic Mapping ====
308 +**12.3.4.1 Basic Mapping**
279 279  
280 280  The main mapping method **from VTL to SDMX** is called **Basic **mapping as well.
281 281  
... ... @@ -299,7 +299,7 @@
299 299  
300 300  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.
301 301  
302 -==== 12.3.4.2 Unpivot Mapping ====
332 +**12.3.4.2 Unpivot Mapping**
303 303  
304 304  An alternative mapping method from VTL to SDMX is the **Unpivot **mapping.
305 305  
... ... @@ -335,7 +335,7 @@
335 335  
336 336  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.
337 337  
338 -==== 12.3.4.3 From VTL Measures to SDMX Data Attributes ====
368 +**12.3.4.3 From VTL Measures to SDMX Data Attributes**
339 339  
340 340  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”).
341 341  
... ... @@ -352,7 +352,9 @@
352 352  
353 353  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.
354 354  
355 -=== 12.3.5 Declaration of the mapping methods between data structures ===
385 +1.
386 +11.
387 +111. Declaration of the mapping methods between data structures
356 356  
357 357  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.
358 358  
... ... @@ -362,10 +362,14 @@
362 362  
363 363  The VtlMappingScheme is a container for zero or more VtlDataflowMapping (it may contain also mappings towards artefacts other than dataflows).
364 364  
365 -=== 12.3.6 Mapping dataflow subsets to distinct VTL Data Sets ===
397 +1.
398 +11.
399 +111. Mapping dataflow subsets to distinct VTL Data Sets
366 366  
367 -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).
401 +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
368 368  
403 +(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).
404 +
369 369  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}}
370 370  
371 371  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}}
... ... @@ -458,10 +458,13 @@
458 458  Some examples follow, for some specific values of INDICATOR and COUNTRY:
459 459  
460 460  ‘DF2(1.0.0)/GDPPERCAPITA.USA’ <- expression11; ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ <- expression12;
497 +
461 461  … … …
462 462  
463 463  ‘DF2(1.0.0)/POPGROWTH.USA’ <- expression21;
501 +
464 464  ‘DF2(1.0.0)/POPGROWTH.CANADA’ <- expression22;
503 +
465 465  … … …
466 466  
467 467  As said, it is assumed that these VTL derived Data Sets have the TIME_PERIOD as the only identifier. In the mapping from VTL to SMDX, the Dimensions INDICATOR and COUNTRY are added to the VTL data structure on order to obtain the SDMX one, with the following values respectively:
... ... @@ -468,9 +468,13 @@
468 468  
469 469  VTL dataset   INDICATOR value COUNTRY value
470 470  
510 +
471 471  ‘DF2(1.0.0)/GDPPERCAPITA.USA’ GDPPERCAPITA USA
512 +
472 472  ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ GDPPERCAPITA CANADA … … …
514 +
473 473  ‘DF2(1.0.0)/POPGROWTH.USA’  POPGROWTH USA
516 +
474 474  ‘DF2(1.0.0)/POPGROWTH.CANADA’ POPGROWTH CANADA
475 475  
476 476  … … …
... ... @@ -478,15 +478,25 @@
478 478  It should be noted that the application of this many-to-one mapping from VTL to SDMX is equivalent to an appropriate sequence of VTL Transformations. These use the VTL operator “calc” to add the proper VTL identifiers (in the example, INDICATOR and COUNTRY) and to assign to them the proper values and the operator “union” in order to obtain the final VTL dataset (in the example DF2(1.0.0)), that can be mapped oneto-one to the homonymous SDMX Dataflow. Following the same example, these VTL Transformations would be:
479 479  
480 480  DF2bis_GDPPERCAPITA_USA := ‘DF2(1.0.0)/GDPPERCAPITA.USA’ [calc identifier INDICATOR := ”GDPPERCAPITA”, identifier COUNTRY := ”USA”];
524 +
481 481  DF2bis_GDPPERCAPITA_CANADA := ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ [calc identifier INDICATOR:=”GDPPERCAPITA”, identifier COUNTRY:=”CANADA”]; … … …
526 +
482 482  DF2bis_POPGROWTH_USA := ‘DF2(1.0.0)/POPGROWTH.USA’
528 +
483 483  [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”USA”];
530 +
484 484  DF2bis_POPGROWTH_CANADA’ := ‘DF2(1.0.0)/POPGROWTH.CANADA’ [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”CANADA”]; … … …
532 +
485 485  DF2(1.0) <- UNION  (DF2bis_GDPPERCAPITA_USA’,
534 +
486 486  DF2bis_GDPPERCAPITA_CANADA’,
536 +
487 487  … ,
538 +
488 488  DF2bis_POPGROWTH_USA’,
540 +
489 489  DF2bis_POPGROWTH_CANADA’
542 +
490 490  …);
491 491  
492 492  In other words, starting from the datasets explicitly calculated through VTL (in the example ‘DF2(1.0)/GDPPERCAPITA.USA’ and so on), the first step consists in calculating other (non-persistent) VTL datasets (in the example DF2bis_GDPPERCAPITA_USA and so on) by adding the identifiers INDICATOR and COUNTRY with the desired values (//INDICATORvalue// and //COUNTRYvalue)//. Finally, all these non-persistent Data Sets are united and give the final result DF2(1.0){{footnote}}The result is persistent in this example but it can be also non persistent if needed.{{/footnote}}, which can be mapped one-to-one to the homonymous SDMX Dataflow having the dimension components TIME_PERIOD, INDICATOR and COUNTRY.
... ... @@ -495,7 +495,9 @@
495 495  
496 496  It is worth noting that in the direction from VTL to SDMX it is mandatory to specify the value for every Dimension on which the mapping is based (in other word, in the name of the calculated VTL dataset is not possible to omit the value of some of the Dimensions).
497 497  
498 -=== 12.3.7 Mapping variables and value domains between VTL and SDMX ===
551 +1.
552 +11.
553 +111. Mapping variables and value domains between VTL and SDMX
499 499  
500 500  With reference to the VTL “model for Variables and Value domains”, the following additional mappings have to be considered:
501 501  
... ... @@ -504,6 +504,7 @@
504 504  |**Represented Variable**|**Concept** with a definite Representation
505 505  |**Value Domain**|(((
506 506  **Representation** (see the Structure
562 +
507 507  Pattern in the Base Package)
508 508  )))
509 509  |**Enumerated Value Domain / Code List**|**Codelist**
... ... @@ -510,6 +510,7 @@
510 510  |**Code**|**Code** (for enumerated DimensionComponent, Measure, DataAttribute)
511 511  |**Described Value Domain**|(((
512 512  non-enumerated** Representation**
569 +
513 513  (having Facets / ExtendedFacets, see the Structure Pattern in the Base Package)
514 514  )))
515 515  |**Value**|Although this abstraction exists in SDMX, it does not have an explicit definition and correspond to a **Code** of a Codelist (for enumerated Representations) or
... ... @@ -533,10 +533,10 @@
533 533  
534 534  It remains up to the SDMX-VTL definer also the assurance of the consistency between a VTL Ruleset defined on Variables and the SDMX Components on which the Ruleset is applied. In fact, a VTL Ruleset is expressed by means of the values of the Variables (i.e. SDMX Concepts), i.e. assuming definite representations for them (e.g. ISOalpha-3 for country). If the Ruleset is applied to SDMX Components that have the same name of the Concept they refer to but different representations (e.g. ISO-alpha-2 for country), the Ruleset cannot work properly.
535 535  
536 -== 12.4 Mapping between SDMX and VTL Data Types ==
593 +1.
594 +11. Mapping between SDMX and VTL Data Types
595 +111. VTL Data types
537 537  
538 -=== 12.4.1 VTL Data types ===
539 -
540 540  According to the VTL User Guide the possible operations in VTL depend on the data types of the artefacts. For example, numbers can be multiplied but text strings cannot. In the VTL Transformations, the compliance between the operators and the data types of their operands is statically checked, i.e., violations result in compile-time errors.
541 541  
542 542  The VTL data types are sub-divided in scalar types (like integers, strings, etc.), which are the types of the scalar values, and compound types (like Data Sets, Components, Rulesets, etc.), which are the types of the compound structures. See below the diagram of the VTL data types, taken from the VTL User Manual:
... ... @@ -543,15 +543,17 @@
543 543  
544 544  [[image:1750067055028-964.png]]
545 545  
546 -**Figure 22 – VTL Data Types**
603 +==== Figure 22 – VTL Data Types ====
547 547  
548 548  The VTL scalar types are in turn subdivided in basic scalar types, which are elementary (not defined in term of other data types) and Value Domain and Set scalar types, which are defined in terms of the basic scalar types.
549 549  
550 550  The VTL basic scalar types are listed below and follow a hierarchical structure in terms of supersets/subsets (e.g. "scalar" is the superset of all the basic scalar types):
551 551  
552 -**Figure 23 – VTL Basic Scalar Types**
609 +==== Figure 23 – VTL Basic Scalar Types ====
553 553  
554 -=== 12.4.2 VTL basic scalar types and SDMX data types ===
611 +1.
612 +11.
613 +111. VTL basic scalar types and SDMX data types
555 555  
556 556  The VTL assumes that a basic scalar type has a unique internal representation and can have more external representations.
557 557  
... ... @@ -569,7 +569,9 @@
569 569  
570 570  The opposite conversion, i.e. from VTL to SDMX, happens when a VTL result, i.e. a VTL Data Set output of a Transformation, must become a SDMX artefact (or part of it). The values of the VTL result must be converted into the desired (SDMX) external representations (data types) of the SDMX artefact.
571 571  
572 -=== 12.4.3 Mapping SDMX data types to VTL basic scalar types ===
631 +1.
632 +11.
633 +111. Mapping SDMX data types to VTL basic scalar types
573 573  
574 574  The following table describes the default mapping for converting from the SDMX data types to the VTL basic scalar types.
575 575  
... ... @@ -576,6 +576,7 @@
576 576  |SDMX data type (BasicComponentDataType)|Default VTL basic scalar type
577 577  |(((
578 578  String
640 +
579 579  (string allowing any character)
580 580  )))|string
581 581  |(((
... ... @@ -585,6 +585,7 @@
585 585  )))|string
586 586  |(((
587 587  AlphaNumeric
650 +
588 588  (string which only allows A-z and 0-9)
589 589  )))|string
590 590  |(((
... ... @@ -594,70 +594,89 @@
594 594  )))|string
595 595  |(((
596 596  BigInteger
660 +
597 597  (corresponds to XML Schema xs:integer datatype; infinite set of integer values)
598 598  )))|integer
599 599  |(((
600 600  Integer
665 +
601 601  (corresponds to XML Schema xs:int datatype; between -2147483648 and +2147483647
667 +
602 602  (inclusive))
603 603  )))|integer
604 604  |(((
605 605  Long
672 +
606 606  (corresponds to XML Schema xs:long datatype; between -9223372036854775808 and
674 +
607 607  +9223372036854775807 (inclusive))
608 608  )))|integer
609 609  |(((
610 610  Short
679 +
611 611  (corresponds to XML Schema xs:short datatype; between -32768 and -32767 (inclusive))
612 612  )))|integer
613 613  |Decimal (corresponds to XML Schema xs:decimal datatype; subset of real numbers that can be represented as decimals)|number
614 614  |(((
615 615  Float
685 +
616 616  (corresponds to XML Schema xs:float datatype; patterned after the IEEE single-precision 32-bit floating point type)
617 617  )))|number
618 618  |(((
619 619  Double
690 +
620 620  (corresponds to XML Schema xs:double datatype; patterned after the IEEE double-precision 64-bit floating point type)
621 621  )))|number
622 622  |(((
623 623  Boolean
695 +
624 624  (corresponds to the XML Schema xs:boolean datatype; support the mathematical concept of
697 +
625 625  binary-valued logic: {true, false})
626 626  )))|boolean
627 627  |(((
628 628  URI
702 +
629 629  (corresponds to the XML Schema xs:anyURI; absolute or relative Uniform Resource Identifier Reference)
630 630  )))|string
631 631  |(((
632 632  Count
707 +
633 633  (an integer following a sequential pattern, increasing by 1 for each occurrence)
634 634  )))|integer
635 635  |(((
636 636  InclusiveValueRange
712 +
637 637  (decimal number within a closed interval, whose bounds are specified in the SDMX representation by the facets minValue and maxValue)
638 638  )))|number
639 639  |(((
640 640  ExclusiveValueRange
717 +
641 641  (decimal number within an open interval, whose bounds are specified in the SDMX representation by the facets minValue and maxValue)
642 642  )))|number
643 643  |(((
644 644  Incremental
722 +
645 645  (decimal number the increased by a specific interval (defined by the interval facet), which is typically enforced outside of the XML validation)
646 646  )))|number
647 647  |(((
648 648  ObservationalTimePeriod
727 +
649 649  (superset of StandardTimePeriod and TimeRange)
650 650  )))|time
651 651  |(((
652 652  StandardTimePeriod
732 +
653 653  (superset of BasicTimePeriod and ReportingTimePeriod)
654 654  )))|time
655 655  |(((
656 656  BasicTimePeriod
737 +
657 657  (superset of GregorianTimePeriod and DateTime)
658 658  )))|date
659 659  |(((
660 660  GregorianTimePeriod
742 +
661 661  (superset of GregorianYear, GregorianYearMonth, and GregorianDay)
662 662  )))|date
663 663  |GregorianYear (YYYY)|date
... ... @@ -665,26 +665,32 @@
665 665  |GregorianDay (YYYY-MM-DD)|date
666 666  |(((
667 667  ReportingTimePeriod
750 +
668 668  (superset of RepostingYear, ReportingSemester, ReportingTrimester, ReportingQuarter, ReportingMonth, ReportingWeek, ReportingDay)
669 669  )))|time_period
670 670  |(((
671 671  ReportingYear
755 +
672 672  (YYYY-A1 – 1 year period)
673 673  )))|time_period
674 674  |(((
675 675  ReportingSemester
760 +
676 676  (YYYY-Ss – 6 month period)
677 677  )))|time_period
678 678  |(((
679 679  ReportingTrimester
765 +
680 680  (YYYY-Tt – 4 month period)
681 681  )))|time_period
682 682  |(((
683 683  ReportingQuarter
770 +
684 684  (YYYY-Qq – 3 month period)
685 685  )))|time_period
686 686  |(((
687 687  ReportingMonth
775 +
688 688  (YYYY-Mmm – 1 month period)
689 689  )))|time_period
690 690  |ReportingWeek|time_period
... ... @@ -691,34 +691,42 @@
691 691  | (YYYY-Www – 7 day period; following ISO 8601 definition of a week in a year)|
692 692  |(((
693 693  ReportingDay
782 +
694 694  (YYYY-Dddd – 1 day period)
695 695  )))|time_period
696 696  |(((
697 697  DateTime
787 +
698 698  (YYYY-MM-DDThh:mm:ss)
699 699  )))|date
700 700  |(((
701 701  TimeRange
792 +
702 702  (YYYY-MM-DD(Thh:mm:ss)?/<duration>)
703 703  )))|time
704 704  |(((
705 705  Month
797 +
706 706  (~-~-MM; speicifies a month independent of a year; e.g. February is black history month in the United States)
707 707  )))|string
708 708  |(((
709 709  MonthDay
802 +
710 710  (~-~-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)
711 711  )))|string
712 712  |(((
713 713  Day
807 +
714 714  (~-~--DD; specifies a day independent of a month or year; e.g. the 15^^th^^ is payday)
715 715  )))|string
716 716  |(((
717 717  Time
812 +
718 718  (hh:mm:ss; time independent of a date; e.g. coffee break is at 10:00 AM)
719 719  )))|string
720 720  |(((
721 721  Duration
817 +
722 722  (corresponds to XML Schema xs:duration datatype)
723 723  )))|duration
724 724  |XHTML|Metadata type – not applicable
... ... @@ -726,20 +726,27 @@
726 726  |IdentifiableReference|Metadata type – not applicable
727 727  |DataSetReference|Metadata type – not applicable
728 728  
729 -**Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types**
825 +додол
730 730  
827 +==== Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types ====
828 +
731 731  When VTL takes in input SDMX artefacts, it is assumed that a type conversion according to the table above always happens. In case a different VTL basic scalar type is desired, it can be achieved in the VTL program taking in input the default VTL basic scalar type above and applying to it the VTL type conversion features (see the implicit and explicit type conversion and the "cast" operator in the VTL Reference Manual).
732 732  
733 -=== 12.4.4 Mapping VTL basic scalar types to SDMX data types ===
831 +1.
832 +11.
833 +111. Mapping VTL basic scalar types to SDMX data types
734 734  
735 735  The following table describes the default conversion from the VTL basic scalar types to the SDMX data types .
736 736  
737 737  |(((
738 738  VTL basic
839 +
739 739  scalar type
740 740  )))|(((
741 741  Default SDMX data type
843 +
742 742  (BasicComponentDataType
845 +
743 743  )
744 744  )))|Default output format
745 745  |String|String|Like XML (xs:string)
... ... @@ -749,15 +749,17 @@
749 749  |Time|StandardTimePeriod|<date>/<date> (as defined above)
750 750  |time_period|(((
751 751  ReportingTimePeriod
855 +
752 752  (StandardReportingPeriod)
753 753  )))|(((
754 754   YYYY-Pppp
859 +
755 755  (according to SDMX )
756 756  )))
757 757  |Duration|Duration|Like XML (xs:duration) PnYnMnDTnHnMnS
758 758  |Boolean|Boolean|Like XML (xs:boolean) with the values "true" or "false"
759 759  
760 -**Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types**
865 +==== Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types ====
761 761  
762 762  In case a different default conversion is desired, it can be achieved through the CustomTypeScheme and CustomType artefacts (see also the section
763 763  
... ... @@ -815,13 +815,17 @@
815 815  
816 816  The default conversion, either standard or customized, can be used to deduce automatically the representation of the components of the result of a VTL Transformation. In alternative, the representation of the resulting SDMX Dataflow can be given explicitly by providing its DataStructureDefinition. In other words, the representation specified in the DSD, if available, overrides any default conversion{{footnote}}The representation given in the DSD should obviously be compatible with the VTL data type.{{/footnote}}.
817 817  
818 -=== 12.4.3 Null Values ===
923 +1.
924 +11.
925 +111. Null Values
819 819  
820 820  In the conversions from SDMX to VTL it is assumed by default that a missing value in SDMX becomes a NULL in VTL. After the conversion, the NULLs can be manipulated through the proper VTL operators.
821 821  
822 822  On the other side, the VTL programs can produce in output NULL values for Measures and Attributes (Null values are not allowed in the Identifiers). In the conversion from VTL to SDMX, it is assumed that a NULL in VTL becomes a missing value in SDMX. In the conversion from VTL to SDMX, the default assumption can be overridden, separately for each VTL basic scalar type, by specifying which the value that represents the NULL in SDMX is. This can be specified in the attribute "nullValue" of the CustomType artefact (see also the section Transformations and Expressions of the SDMX information model). A CustomType belongs to a CustomTypeScheme, which can be referenced by one or more TransformationScheme (i.e. VTL programs). The overriding assumption is applied for all the SDMX Dataflows calculated in the TransformationScheme.
823 823  
824 -=== 12.4.5 Format of the literals used in VTL Transformations ===
931 +1.
932 +11.
933 +111. Format of the literals used in VTL Transformations
825 825  
826 826  The VTL programs can contain literals, i.e. specific values of certain data types written directly in the VTL definitions or expressions. The VTL does not prescribe a specific format for the literals and leave the specific VTL systems and the definers of VTL Transformations free of using their preferred formats.
827 827  
... ... @@ -835,6 +835,42 @@
835 835  
836 836  In case a literal is operand of a VTL Cast operation, the format specified in the Cast overrides all the possible otherwise specified formats.
837 837  
947 +
838 838  ----
839 839  
950 +[[~[1~]>>path:#_ftnref1]] 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>>url:https://sdmx.org/]][[.>>url:https://sdmx.org/]]
951 +
952 +[[~[2~]>>path:#_ftnref2]] In this chapter, in order to distinguish VTL and SDMX model artefacts, the VTL ones are written in the Arial font while the SDMX ones in Courier New
953 +
954 +[[~[3~]>>path:#_ftnref3]] See also the section "VTL-DL Rulesets" in the VTL Reference Manual.
955 +
956 +[[~[4~]>>path:#_ftnref4]] The VTLMappings are used also for User Defined Operators (UDO). Although UDOs are envisaged to be defined on generic operands, so that the specific artefacts to be manipulated are passed as parameters at their invocation, it is also possible that an UDO invokes directly some specific SDMX artefacts. These SDMX artefacts have to be mapped to the corresponding aliases used in the definition of the UDO through the VtlMappingScheme and VtlMapping classes as well.
957 +
958 +[[~[5~]>>path:#_ftnref5]] 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)").
959 +
960 +[[~[6~]>>path:#_ftnref6]] The container-object-id can repeat and may not be present.
961 +
962 +[[~[7~]>>path:#_ftnref7]] i.e., the artefact belongs to a maintainable class
963 +
964 +[[~[8~]>>path:#_ftnref8]] 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.
965 +
966 +[[~[9~]>>path:#_ftnref9]] For the syntax of the VTL operators see the VTL Reference Manual
967 +
968 +[[~[10~]>>path:#_ftnref10]] In case the invoked artefact is a VTL component, which can be invoked only within the invocation of a VTL data set (SDMX Dataflow), the specific SDMX class-name (e.g. Dimension, TimeDimension, Measure or DataAttribute) can be deduced from the data structure of the SDMX Dataflow, which the component belongs to.
969 +
970 +[[~[11~]>>path:#_ftnref11]] 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)
971 +
972 +[[~[12~]>>path:#_ftnref12]] Single quotes are needed because this reference is not a VTL regular name. ^^19^^ Single quotes are not needed in this case because CL_FREQ is a VTL regular name.
973 +
974 +[[~[13~]>>path:#_ftnref13]] The result DFR(1.0.0) is be equal to DF1(1.0.0) save that the component SECTOR is called SEC
975 +
976 +[[~[14~]>>path:#_ftnref14]] Rulesets of this kind cannot be reused when the referenced Concept has a different representation.
977 +
978 +[[~[15~]>>path:#_ftnref15]] See also the section "VTL-DL Rulesets" in the VTL Reference Manual.
979 +
980 +[[~[16~]>>path:#_ftnref16]] If a calculated artefact is persistent, it needs a persistent definition, i.e. a SDMX definition in a SDMX environment. In addition, possible calculated artefact that are not persistent may require a SDMX definition, for example when the result of a nonpersistent calculation is disseminated through SDMX tools (like an inquiry tool).
981 +
982 +[[~[17~]>>path:#_ftnref17]] See the VTL 2.0 User Manual
983 +
984 +
840 840  {{putFootnotes/}}