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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.
... ... @@ -92,14 +92,15 @@
92 92  
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 -** "datastructure" for the classes Dataflow, Dimension, TimeDimension, Measure, DataAttribute,
96 -** "conceptscheme" for the class Concept,
97 -** "codelist" for the class Codelist.
98 -* 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}}.
99 -* 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).
100 -* As for the maintainedobject-id, this is essential in some cases while in other cases it can be omitted:
101 -** if the referenced artefact is a Dataflow, which is a maintainable class, the maintainedobject-id is the dataflow-id and obviously cannot be omitted;
102 -** 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;
107 +** "datastructure" for the classes Dataflow, Dimension, TimeDimension, Measure, DataAttribute, o "conceptscheme" for the class Concept, o "codelist" for the class Codelist.
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).
110 +* 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;
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 +*
103 103  ** 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;
104 104  ** if the referenced artefact is a Codelist, which is a maintainable class, the maintainedobject-id is the codelist-id and obviously cannot be omitted.
105 105  * 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.
... ... @@ -120,7 +120,7 @@
120 120  
121 121  DFR := DF1 + DF2
122 122  
123 -The references to the Codelists can be simplified similarly. For example, given the non-abbreviated reference to the Codelist AG:CL_FREQ(1.0.0), which is{{footnote}}Single quotes are needed because this reference is not a VTL regular name. 19 Single quotes are not needed in this case because CL_FREQ is a VTL regular name.{{/footnote}}:
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]](%%):
124 124  
125 125  'urn:sdmx:org.sdmx.infomodel.codelist.Codelist=AG:CL_FREQ(1.0.0)'
126 126  
... ... @@ -138,7 +138,7 @@
138 138  
139 139  SECTOR
140 140  
141 -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]](%%):
142 142  
143 143  'DFR(1.0.0)' := 'DF1(1.0.0)' [rename SECTOR to SEC]
144 144  
... ... @@ -158,37 +158,43 @@
158 158  
159 159  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).
160 160  
161 -=== 12.2.4 User-defined alias ===
174 +1.
175 +11.
176 +111. User-defined alias
162 162  
163 163  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.
164 164  
165 165  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).
166 166  
167 -=== 12.2.5 References to SDMX artefacts from VTL Rulesets ===
182 +1.
183 +11.
184 +111. References to SDMX artefacts from VTL Rulesets
168 168  
169 169  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.
170 170  
171 171  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.
172 172  
173 -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]](%%).
174 174  
175 -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]]
176 176  
177 177  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.
178 178  
179 -== 12.3 Mapping between SDMX and VTL artefacts ==
196 +1.
197 +11. Mapping between SDMX and VTL artefacts
198 +111. When the mapping occurs
180 180  
181 -=== 12.3.1. When the mapping occurs ===
182 -
183 183  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.
184 184  
185 -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]](%%).
186 186  
187 187  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).
188 188  
189 -=== 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
190 190  
191 -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}}.
192 192  
193 193  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}}
194 194  
... ... @@ -202,9 +202,11 @@
202 202  
203 203  The possible mapping options are described in more detail in the following sections.
204 204  
205 -=== 12.3.2 Mapping from SDMX to VTL data structures ===
224 +1.
225 +11.
226 +111. Mapping from SDMX to VTL data structures
206 206  
207 -==== 12.3.3.1 Basic Mapping ====
228 +**12.3.3.1 Basic Mapping**
208 208  
209 209  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.
210 210  
... ... @@ -220,7 +220,7 @@
220 220  
221 221  With the Basic mapping, one SDMX observation^^27^^ generates one VTL data point.
222 222  
223 -==== 12.3.3.2 Pivot Mapping ====
244 +**12.3.3.2 Pivot Mapping**
224 224  
225 225  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.
226 226  
... ... @@ -251,6 +251,7 @@
251 251  |DataAttribute not depending on the MeasureDimension|Attribute
252 252  |DataAttribute depending on the MeasureDimension|(((
253 253  One Attribute for each Code of the
275 +
254 254  SDMX MeasureDimension
255 255  )))
256 256  
... ... @@ -263,10 +263,13 @@
263 263  
264 264  Identifiers, (time) Identifier and Attributes.
265 265  
266 -* 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 +
267 267  * 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
268 268  
269 -==== 12.3.3.3 From SDMX DataAttributes to VTL Measures ====
294 +**12.3.3.3 From SDMX DataAttributes to VTL Measures**
270 270  
271 271  * 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
272 272  
... ... @@ -276,9 +276,11 @@
276 276  
277 277  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.
278 278  
279 -=== 12.3.4 Mapping from VTL to SDMX data structures ===
304 +1.
305 +11.
306 +111. Mapping from VTL to SDMX data structures
280 280  
281 -==== 12.3.4.1 Basic Mapping ====
308 +**12.3.4.1 Basic Mapping**
282 282  
283 283  The main mapping method **from VTL to SDMX** is called **Basic **mapping as well.
284 284  
... ... @@ -302,7 +302,7 @@
302 302  
303 303  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.
304 304  
305 -==== 12.3.4.2 Unpivot Mapping ====
332 +**12.3.4.2 Unpivot Mapping**
306 306  
307 307  An alternative mapping method from VTL to SDMX is the **Unpivot **mapping.
308 308  
... ... @@ -338,7 +338,7 @@
338 338  
339 339  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.
340 340  
341 -==== 12.3.4.3 From VTL Measures to SDMX Data Attributes ====
368 +**12.3.4.3 From VTL Measures to SDMX Data Attributes**
342 342  
343 343  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”).
344 344  
... ... @@ -355,7 +355,9 @@
355 355  
356 356  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.
357 357  
358 -=== 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
359 359  
360 360  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.
361 361  
... ... @@ -365,10 +365,14 @@
365 365  
366 366  The VtlMappingScheme is a container for zero or more VtlDataflowMapping (it may contain also mappings towards artefacts other than dataflows).
367 367  
368 -=== 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
369 369  
370 -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
371 371  
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 +
372 372  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}}
373 373  
374 374  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}}
... ... @@ -461,10 +461,13 @@
461 461  Some examples follow, for some specific values of INDICATOR and COUNTRY:
462 462  
463 463  ‘DF2(1.0.0)/GDPPERCAPITA.USA’ <- expression11; ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ <- expression12;
497 +
464 464  … … …
465 465  
466 466  ‘DF2(1.0.0)/POPGROWTH.USA’ <- expression21;
501 +
467 467  ‘DF2(1.0.0)/POPGROWTH.CANADA’ <- expression22;
503 +
468 468  … … …
469 469  
470 470  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:
... ... @@ -471,9 +471,13 @@
471 471  
472 472  VTL dataset   INDICATOR value COUNTRY value
473 473  
510 +
474 474  ‘DF2(1.0.0)/GDPPERCAPITA.USA’ GDPPERCAPITA USA
512 +
475 475  ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ GDPPERCAPITA CANADA … … …
514 +
476 476  ‘DF2(1.0.0)/POPGROWTH.USA’  POPGROWTH USA
516 +
477 477  ‘DF2(1.0.0)/POPGROWTH.CANADA’ POPGROWTH CANADA
478 478  
479 479  … … …
... ... @@ -481,15 +481,25 @@
481 481  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:
482 482  
483 483  DF2bis_GDPPERCAPITA_USA := ‘DF2(1.0.0)/GDPPERCAPITA.USA’ [calc identifier INDICATOR := ”GDPPERCAPITA”, identifier COUNTRY := ”USA”];
524 +
484 484  DF2bis_GDPPERCAPITA_CANADA := ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ [calc identifier INDICATOR:=”GDPPERCAPITA”, identifier COUNTRY:=”CANADA”]; … … …
526 +
485 485  DF2bis_POPGROWTH_USA := ‘DF2(1.0.0)/POPGROWTH.USA’
528 +
486 486  [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”USA”];
530 +
487 487  DF2bis_POPGROWTH_CANADA’ := ‘DF2(1.0.0)/POPGROWTH.CANADA’ [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”CANADA”]; … … …
532 +
488 488  DF2(1.0) <- UNION  (DF2bis_GDPPERCAPITA_USA’,
534 +
489 489  DF2bis_GDPPERCAPITA_CANADA’,
536 +
490 490  … ,
538 +
491 491  DF2bis_POPGROWTH_USA’,
540 +
492 492  DF2bis_POPGROWTH_CANADA’
542 +
493 493  …);
494 494  
495 495  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.
... ... @@ -498,7 +498,9 @@
498 498  
499 499  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).
500 500  
501 -=== 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
502 502  
503 503  With reference to the VTL “model for Variables and Value domains”, the following additional mappings have to be considered:
504 504  
... ... @@ -507,6 +507,7 @@
507 507  |**Represented Variable**|**Concept** with a definite Representation
508 508  |**Value Domain**|(((
509 509  **Representation** (see the Structure
562 +
510 510  Pattern in the Base Package)
511 511  )))
512 512  |**Enumerated Value Domain / Code List**|**Codelist**
... ... @@ -513,6 +513,7 @@
513 513  |**Code**|**Code** (for enumerated DimensionComponent, Measure, DataAttribute)
514 514  |**Described Value Domain**|(((
515 515  non-enumerated** Representation**
569 +
516 516  (having Facets / ExtendedFacets, see the Structure Pattern in the Base Package)
517 517  )))
518 518  |**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
... ... @@ -536,10 +536,10 @@
536 536  
537 537  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.
538 538  
539 -== 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
540 540  
541 -=== 12.4.1 VTL Data types ===
542 -
543 543  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.
544 544  
545 545  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:
... ... @@ -546,15 +546,17 @@
546 546  
547 547  [[image:1750067055028-964.png]]
548 548  
549 -**Figure 22 – VTL Data Types**
603 +==== Figure 22 – VTL Data Types ====
550 550  
551 551  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.
552 552  
553 553  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):
554 554  
555 -**Figure 23 – VTL Basic Scalar Types**
609 +==== Figure 23 – VTL Basic Scalar Types ====
556 556  
557 -=== 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
558 558  
559 559  The VTL assumes that a basic scalar type has a unique internal representation and can have more external representations.
560 560  
... ... @@ -572,7 +572,9 @@
572 572  
573 573  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.
574 574  
575 -=== 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
576 576  
577 577  The following table describes the default mapping for converting from the SDMX data types to the VTL basic scalar types.
578 578  
... ... @@ -579,6 +579,7 @@
579 579  |SDMX data type (BasicComponentDataType)|Default VTL basic scalar type
580 580  |(((
581 581  String
640 +
582 582  (string allowing any character)
583 583  )))|string
584 584  |(((
... ... @@ -588,6 +588,7 @@
588 588  )))|string
589 589  |(((
590 590  AlphaNumeric
650 +
591 591  (string which only allows A-z and 0-9)
592 592  )))|string
593 593  |(((
... ... @@ -597,70 +597,89 @@
597 597  )))|string
598 598  |(((
599 599  BigInteger
660 +
600 600  (corresponds to XML Schema xs:integer datatype; infinite set of integer values)
601 601  )))|integer
602 602  |(((
603 603  Integer
665 +
604 604  (corresponds to XML Schema xs:int datatype; between -2147483648 and +2147483647
667 +
605 605  (inclusive))
606 606  )))|integer
607 607  |(((
608 608  Long
672 +
609 609  (corresponds to XML Schema xs:long datatype; between -9223372036854775808 and
674 +
610 610  +9223372036854775807 (inclusive))
611 611  )))|integer
612 612  |(((
613 613  Short
679 +
614 614  (corresponds to XML Schema xs:short datatype; between -32768 and -32767 (inclusive))
615 615  )))|integer
616 616  |Decimal (corresponds to XML Schema xs:decimal datatype; subset of real numbers that can be represented as decimals)|number
617 617  |(((
618 618  Float
685 +
619 619  (corresponds to XML Schema xs:float datatype; patterned after the IEEE single-precision 32-bit floating point type)
620 620  )))|number
621 621  |(((
622 622  Double
690 +
623 623  (corresponds to XML Schema xs:double datatype; patterned after the IEEE double-precision 64-bit floating point type)
624 624  )))|number
625 625  |(((
626 626  Boolean
695 +
627 627  (corresponds to the XML Schema xs:boolean datatype; support the mathematical concept of
697 +
628 628  binary-valued logic: {true, false})
629 629  )))|boolean
630 630  |(((
631 631  URI
702 +
632 632  (corresponds to the XML Schema xs:anyURI; absolute or relative Uniform Resource Identifier Reference)
633 633  )))|string
634 634  |(((
635 635  Count
707 +
636 636  (an integer following a sequential pattern, increasing by 1 for each occurrence)
637 637  )))|integer
638 638  |(((
639 639  InclusiveValueRange
712 +
640 640  (decimal number within a closed interval, whose bounds are specified in the SDMX representation by the facets minValue and maxValue)
641 641  )))|number
642 642  |(((
643 643  ExclusiveValueRange
717 +
644 644  (decimal number within an open interval, whose bounds are specified in the SDMX representation by the facets minValue and maxValue)
645 645  )))|number
646 646  |(((
647 647  Incremental
722 +
648 648  (decimal number the increased by a specific interval (defined by the interval facet), which is typically enforced outside of the XML validation)
649 649  )))|number
650 650  |(((
651 651  ObservationalTimePeriod
727 +
652 652  (superset of StandardTimePeriod and TimeRange)
653 653  )))|time
654 654  |(((
655 655  StandardTimePeriod
732 +
656 656  (superset of BasicTimePeriod and ReportingTimePeriod)
657 657  )))|time
658 658  |(((
659 659  BasicTimePeriod
737 +
660 660  (superset of GregorianTimePeriod and DateTime)
661 661  )))|date
662 662  |(((
663 663  GregorianTimePeriod
742 +
664 664  (superset of GregorianYear, GregorianYearMonth, and GregorianDay)
665 665  )))|date
666 666  |GregorianYear (YYYY)|date
... ... @@ -668,26 +668,32 @@
668 668  |GregorianDay (YYYY-MM-DD)|date
669 669  |(((
670 670  ReportingTimePeriod
750 +
671 671  (superset of RepostingYear, ReportingSemester, ReportingTrimester, ReportingQuarter, ReportingMonth, ReportingWeek, ReportingDay)
672 672  )))|time_period
673 673  |(((
674 674  ReportingYear
755 +
675 675  (YYYY-A1 – 1 year period)
676 676  )))|time_period
677 677  |(((
678 678  ReportingSemester
760 +
679 679  (YYYY-Ss – 6 month period)
680 680  )))|time_period
681 681  |(((
682 682  ReportingTrimester
765 +
683 683  (YYYY-Tt – 4 month period)
684 684  )))|time_period
685 685  |(((
686 686  ReportingQuarter
770 +
687 687  (YYYY-Qq – 3 month period)
688 688  )))|time_period
689 689  |(((
690 690  ReportingMonth
775 +
691 691  (YYYY-Mmm – 1 month period)
692 692  )))|time_period
693 693  |ReportingWeek|time_period
... ... @@ -694,34 +694,42 @@
694 694  | (YYYY-Www – 7 day period; following ISO 8601 definition of a week in a year)|
695 695  |(((
696 696  ReportingDay
782 +
697 697  (YYYY-Dddd – 1 day period)
698 698  )))|time_period
699 699  |(((
700 700  DateTime
787 +
701 701  (YYYY-MM-DDThh:mm:ss)
702 702  )))|date
703 703  |(((
704 704  TimeRange
792 +
705 705  (YYYY-MM-DD(Thh:mm:ss)?/<duration>)
706 706  )))|time
707 707  |(((
708 708  Month
797 +
709 709  (~-~-MM; speicifies a month independent of a year; e.g. February is black history month in the United States)
710 710  )))|string
711 711  |(((
712 712  MonthDay
802 +
713 713  (~-~-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)
714 714  )))|string
715 715  |(((
716 716  Day
807 +
717 717  (~-~--DD; specifies a day independent of a month or year; e.g. the 15^^th^^ is payday)
718 718  )))|string
719 719  |(((
720 720  Time
812 +
721 721  (hh:mm:ss; time independent of a date; e.g. coffee break is at 10:00 AM)
722 722  )))|string
723 723  |(((
724 724  Duration
817 +
725 725  (corresponds to XML Schema xs:duration datatype)
726 726  )))|duration
727 727  |XHTML|Metadata type – not applicable
... ... @@ -729,20 +729,27 @@
729 729  |IdentifiableReference|Metadata type – not applicable
730 730  |DataSetReference|Metadata type – not applicable
731 731  
732 -**Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types**
825 +додол
733 733  
827 +==== Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types ====
828 +
734 734  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).
735 735  
736 -=== 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
737 737  
738 738  The following table describes the default conversion from the VTL basic scalar types to the SDMX data types .
739 739  
740 740  |(((
741 741  VTL basic
839 +
742 742  scalar type
743 743  )))|(((
744 744  Default SDMX data type
843 +
745 745  (BasicComponentDataType
845 +
746 746  )
747 747  )))|Default output format
748 748  |String|String|Like XML (xs:string)
... ... @@ -752,15 +752,17 @@
752 752  |Time|StandardTimePeriod|<date>/<date> (as defined above)
753 753  |time_period|(((
754 754  ReportingTimePeriod
855 +
755 755  (StandardReportingPeriod)
756 756  )))|(((
757 757   YYYY-Pppp
859 +
758 758  (according to SDMX )
759 759  )))
760 760  |Duration|Duration|Like XML (xs:duration) PnYnMnDTnHnMnS
761 761  |Boolean|Boolean|Like XML (xs:boolean) with the values "true" or "false"
762 762  
763 -**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 ====
764 764  
765 765  In case a different default conversion is desired, it can be achieved through the CustomTypeScheme and CustomType artefacts (see also the section
766 766  
... ... @@ -818,13 +818,17 @@
818 818  
819 819  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}}.
820 820  
821 -=== 12.4.3 Null Values ===
923 +1.
924 +11.
925 +111. Null Values
822 822  
823 823  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.
824 824  
825 825  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.
826 826  
827 -=== 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
828 828  
829 829  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.
830 830  
... ... @@ -838,6 +838,42 @@
838 838  
839 839  In case a literal is operand of a VTL Cast operation, the format specified in the Cast overrides all the possible otherwise specified formats.
840 840  
947 +
841 841  ----
842 842  
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 +
843 843  {{putFootnotes/}}