Changes for page 12 Validation and Transformation Language (VTL)

Last modified by Artur on 2025/09/10 11:19

From 1.12 to 1.11 From 1.19 to 1.18

From version 1.18

edited by Helena
on 2025/06/16 13:24

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To version 1.12

edited by Helena
on 2025/06/16 13:10

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@@ -19,7 +19,6 @@
  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.
  == 12.2  References to SDMX artefacts from VTL statements ==
--
  === 12.2.1 Introduction ===
  The VTL can manipulate SDMX artefacts (or objects) by referencing them through predefined conventional names (aliases).
@@ -49,8 +49,10 @@
  The generic structure of the URN is the following:
--SDMXprefix.SDMX-IM-package-name.class-name=agency-id:maintainedobject-id (maintainedobject-version).*container-object-id.object-id
++SDMXprefix.SDMX-IM-package-name.class-name=agency-id:maintainedobject-id
++(maintainedobject-version).*container-object-id.object-id
++
  The **SDMXprefix** is "urn:sdmx:org", always the same for all SDMX artefacts.
  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".
@@ -71,19 +71,24 @@
  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).
--The container-object-id does not apply to the classes that can be referenced in VTL Transformations, therefore is not present in their URN.
++The container-object-id does not apply to the classes that can be referenced in VTL Transformations, therefore is not present in their URN
  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:
--* 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)
++* 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)
++
  * if the artefact is a Concept (the object-id is the name of the Concept)
  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}}:
--> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' <-
--> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
--> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
++'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' <-
++'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
++
++'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
++
  === 12.2.3 Abbreviation of the URN ===
  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.
@@ -92,13 +92,10 @@
  * 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.
  * 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:
--** "datastructure" for the classes Dataflow, Dimension, TimeDimension, Measure, DataAttribute,
--** "conceptscheme" for the class Concept,
--** "codelist" for the class Codelist.
++** "datastructure" for the classes Dataflow, Dimension, TimeDimension, Measure, DataAttribute, o "conceptscheme" for the class Concept, o "codelist" for the class Codelist.
  * 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}}.
  * 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).
--* As for the maintainedobject-id, this is essential in some cases while in other cases it can be omitted:
--** if the referenced artefact is a Dataflow, which is a maintainable class, the maintainedobject-id is the dataflow-id and obviously cannot be omitted;
++* 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;
  ** 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;
  ** 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;
  ** if the referenced artefact is a Codelist, which is a maintainable class, the maintainedobject-id is the codelist-id and obviously cannot be omitted.
@@ -110,47 +110,51 @@
  For example, the full formulation that uses the complete URN shown at the end of the previous paragraph:
--> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' :=
--> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
--> 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
++'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0.0)' :=
++'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF1(1.0.0)' +
++
++'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0.0)'
++
  by omitting all the non-essential parts would become simply:
--> DFR   : =  DF1 + DF2
++DFR := DF1 + DF2
  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}}:
--> 'urn:sdmx:org.sdmx.infomodel.codelist.Codelist=AG:CL_FREQ(1.0.0)'
++'urn:sdmx:org.sdmx.infomodel.codelist.Codelist=AG:CL_FREQ(1.0.0)'
  if the Codelist is referenced from a RulesetScheme belonging to the agency AG, omitting all the optional parts, the abbreviated reference would become simply^^19^^:
--> CL_FREQ
++CL_FREQ
  As for the references to the components, it can be enough to specify the componentId, given that the dataStructure-Id can be omitted. An example of non-abbreviated reference, if the data structure is DST1 and the component is SECTOR, is the following:
--> 'urn:sdmx:org.sdmx.infomodel.datastructure.DataStructure=AG:DST1(1.0.0).S ECTOR'
++'urn:sdmx:org.sdmx.infomodel.datastructure.DataStructure=AG:DST1(1.0.0).S
++ECTOR'
++
  The corresponding fully abbreviated reference, if made from a TransformationScheme belonging to AG, would become simply:
--> SECTOR
++SECTOR
  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}}:
--> 'DFR(1.0.0)' := 'DF1(1.0.0)' [rename SECTOR to SEC]
++'DFR(1.0.0)' := 'DF1(1.0.0)' [rename SECTOR to SEC]
  In the references to the Concepts, which can exist for example in the definition of the VTL Rulesets, at least the conceptScheme-id and the concept-id must be specified.
  An example of non-abbreviated reference, if the conceptScheme-id is CS1 and the concept-id is SECTOR, is the following:
--> 'urn:sdmx:org.sdmx.infomodel.conceptscheme.Concept=AG:CS1(1.0.0).SECTOR'
++'urn:sdmx:org.sdmx.infomodel.conceptscheme.Concept=AG:CS1(1.0.0).SECTOR'
  The corresponding fully abbreviated reference, if made from a RulesetScheme belonging to AG, would become simply:
--> CS1(1.0.0).SECTOR
++CS1(1.0.0).SECTOR
  The Codes and in general all the Values can be written without any other specification, for example, the transformation to check if the values of the measures of the Dataflow DF1 are between 0 and 25000 can be written like follows:
--> 'DFR(1.0.0)' := between ( 'DF1(1.0.0)', 0, 25000 )
++'DFR(1.0.0)' := between ( 'DF1(1.0.0)', 0, 25000 )
  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).
@@ -173,7 +173,6 @@
  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.
  == 12.3 Mapping between SDMX and VTL artefacts ==
--
  === 12.3.1. When the mapping occurs ===
  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.
@@ -457,10 +457,13 @@
  Some examples follow, for some specific values of INDICATOR and COUNTRY:
  ‘DF2(1.0.0)/GDPPERCAPITA.USA’ <- expression11; ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ <- expression12;
++
  … … …
  ‘DF2(1.0.0)/POPGROWTH.USA’  <- expression21;
++
  ‘DF2(1.0.0)/POPGROWTH.CANADA’ <- expression22;
++
  … … …
  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:
@@ -467,9 +467,13 @@
  VTL dataset   INDICATOR value COUNTRY value
++
  ‘DF2(1.0.0)/GDPPERCAPITA.USA’  GDPPERCAPITA USA
++
  ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ GDPPERCAPITA CANADA … … …
++
  ‘DF2(1.0.0)/POPGROWTH.USA’  POPGROWTH USA
++
  ‘DF2(1.0.0)/POPGROWTH.CANADA’  POPGROWTH CANADA
  … … …
@@ -477,15 +477,25 @@
  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:
  DF2bis_GDPPERCAPITA_USA := ‘DF2(1.0.0)/GDPPERCAPITA.USA’ [calc identifier INDICATOR := ”GDPPERCAPITA”, identifier COUNTRY := ”USA”];
++
  DF2bis_GDPPERCAPITA_CANADA := ‘DF2(1.0.0)/GDPPERCAPITA.CANADA’ [calc identifier INDICATOR:=”GDPPERCAPITA”, identifier COUNTRY:=”CANADA”]; … … …
++
  DF2bis_POPGROWTH_USA  := ‘DF2(1.0.0)/POPGROWTH.USA’
++
  [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”USA”];
++
  DF2bis_POPGROWTH_CANADA’ := ‘DF2(1.0.0)/POPGROWTH.CANADA’ [calc identifier INDICATOR := ”POPGROWTH”, identifier COUNTRY := ”CANADA”]; … … …
++
  DF2(1.0) <- UNION   (DF2bis_GDPPERCAPITA_USA’,
++
  DF2bis_GDPPERCAPITA_CANADA’,
++
  … ,
++
  DF2bis_POPGROWTH_USA’,
++
  DF2bis_POPGROWTH_CANADA’
++
  …);
  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.
@@ -494,7 +494,9 @@
  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).
--=== 12.3.7 Mapping variables and value domains between VTL and SDMX ===
++1.
++11.
++111. Mapping variables and value domains between VTL and SDMX
  With reference to the VTL “model for Variables and Value domains”, the following additional mappings have to be considered:
@@ -503,6 +503,7 @@
  |**Represented Variable**|**Concept** with a definite Representation
  |**Value Domain**|(((
  **Representation** (see the Structure
++
  Pattern in the Base Package)
  )))
  |**Enumerated Value Domain / Code List**|**Codelist**
@@ -509,6 +509,7 @@
  |**Code**|**Code** (for enumerated DimensionComponent, Measure, DataAttribute)
  |**Described Value Domain**|(((
  non-enumerated** Representation**
++
  (having Facets / ExtendedFacets, see the Structure Pattern in the Base Package)
  )))
  |**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
@@ -532,10 +532,10 @@
  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.
--== 12.4 Mapping between SDMX and VTL Data Types ==
++1.
++11. Mapping between SDMX and VTL Data Types
++111. VTL Data types
--=== 12.4.1 VTL Data types ===
--
  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.
  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:
@@ -542,15 +542,17 @@
  [[image:1750067055028-964.png]]
--**Figure 22 – VTL Data Types**
++==== Figure 22 – VTL Data Types ====
  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.
  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):
--**Figure 23 – VTL Basic Scalar Types**
++==== Figure 23 – VTL Basic Scalar Types ====
--=== 12.4.2 VTL basic scalar types and SDMX data types ===
++1.
++11.
++111. VTL basic scalar types and SDMX data types
  The VTL assumes that a basic scalar type has a unique internal representation and can have more external representations.
@@ -568,7 +568,9 @@
  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.
--=== 12.4.3 Mapping SDMX data types to VTL basic scalar types ===
++1.
++11.
++111. Mapping SDMX data types to VTL basic scalar types
  The following table describes the default mapping for converting from the SDMX data types to the VTL basic scalar types.
@@ -575,6 +575,7 @@
  |SDMX data type (BasicComponentDataType)|Default VTL basic scalar type
  |(((
  String
++
  (string allowing any character)
  )))|string
  |(((
@@ -584,6 +584,7 @@
  )))|string
  |(((
  AlphaNumeric
++
  (string which only allows A-z and 0-9)
  )))|string
  |(((
@@ -593,70 +593,89 @@
  )))|string
  |(((
  BigInteger
++
  (corresponds to XML Schema xs:integer datatype; infinite set of integer values)
  )))|integer
  |(((
  Integer
++
  (corresponds to XML Schema xs:int datatype; between -2147483648 and +2147483647
++
  (inclusive))
  )))|integer
  |(((
  Long
++
  (corresponds to XML Schema xs:long datatype; between -9223372036854775808 and
++
  +9223372036854775807 (inclusive))
  )))|integer
  |(((
  Short
++
  (corresponds to XML Schema xs:short datatype; between -32768 and -32767 (inclusive))
  )))|integer
  |Decimal (corresponds to XML Schema xs:decimal datatype; subset of real numbers that can be represented as decimals)|number
  |(((
  Float
++
  (corresponds to XML Schema xs:float datatype; patterned after the IEEE single-precision 32-bit floating point type)
  )))|number
  |(((
  Double
++
  (corresponds to XML Schema xs:double datatype; patterned after the IEEE double-precision 64-bit floating point type)
  )))|number
  |(((
  Boolean
++
  (corresponds to the XML Schema xs:boolean datatype; support the mathematical concept of
++
  binary-valued logic: {true, false})
  )))|boolean
  |(((
  URI
++
  (corresponds to the XML Schema xs:anyURI; absolute or relative Uniform Resource Identifier Reference)
  )))|string
  |(((
  Count
++
  (an integer following a sequential pattern, increasing by 1 for each occurrence)
  )))|integer
  |(((
  InclusiveValueRange
++
  (decimal number within a closed interval, whose bounds are specified in the SDMX representation by the facets minValue and maxValue)
  )))|number
  |(((
  ExclusiveValueRange
++
  (decimal number within an open interval, whose bounds are specified in the SDMX representation by the facets minValue and maxValue)
  )))|number
  |(((
  Incremental
++
  (decimal number the increased by a specific interval (defined by the interval facet), which is typically enforced outside of the XML validation)
  )))|number
  |(((
  ObservationalTimePeriod
++
  (superset of StandardTimePeriod and TimeRange)
  )))|time
  |(((
  StandardTimePeriod
++
  (superset of BasicTimePeriod and ReportingTimePeriod)
  )))|time
  |(((
  BasicTimePeriod
++
  (superset of GregorianTimePeriod and DateTime)
  )))|date
  |(((
  GregorianTimePeriod
++
  (superset of GregorianYear, GregorianYearMonth, and GregorianDay)
  )))|date
  |GregorianYear  (YYYY)|date
@@ -664,26 +664,32 @@
  |GregorianDay (YYYY-MM-DD)|date
  |(((
  ReportingTimePeriod
++
  (superset of RepostingYear, ReportingSemester, ReportingTrimester, ReportingQuarter, ReportingMonth, ReportingWeek, ReportingDay)
  )))|time_period
  |(((
  ReportingYear
++
  (YYYY-A1 – 1 year period)
  )))|time_period
  |(((
  ReportingSemester
++
  (YYYY-Ss – 6 month period)
  )))|time_period
  |(((
  ReportingTrimester
++
  (YYYY-Tt – 4 month period)
  )))|time_period
  |(((
  ReportingQuarter
++
  (YYYY-Qq – 3 month period)
  )))|time_period
  |(((
  ReportingMonth
++
  (YYYY-Mmm – 1 month period)
  )))|time_period
  |ReportingWeek|time_period
@@ -690,34 +690,42 @@
  | (YYYY-Www – 7 day period; following ISO 8601 definition of a week in a year)|
  |(((
  ReportingDay
++
  (YYYY-Dddd – 1 day period)
  )))|time_period
  |(((
  DateTime
++
  (YYYY-MM-DDThh:mm:ss)
  )))|date
  |(((
  TimeRange
++
  (YYYY-MM-DD(Thh:mm:ss)?/<duration>)
  )))|time
  |(((
  Month
++
  (~-~-MM; speicifies a month independent of a year; e.g. February is black history month in the United States)
  )))|string
  |(((
  MonthDay
++
  (~-~-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)
  )))|string
  |(((
  Day
++
  (~-~--DD; specifies a day independent of a month or year; e.g. the 15^^th^^ is payday)
  )))|string
  |(((
  Time
++
  (hh:mm:ss; time independent of a date; e.g. coffee break is at 10:00 AM)
  )))|string
  |(((
  Duration
++
  (corresponds to XML Schema xs:duration datatype)
  )))|duration
  |XHTML|Metadata type – not applicable
@@ -725,20 +725,27 @@
  |IdentifiableReference|Metadata type – not applicable
  |DataSetReference|Metadata type – not applicable
--**Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types**
++додол
++==== Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types ====
++
  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).
--=== 12.4.4 Mapping VTL basic scalar types to SDMX data types ===
++1.
++11.
++111. Mapping VTL basic scalar types to SDMX data types
  The following table describes the default conversion from the VTL basic scalar types to the SDMX data types .
  |(((
  VTL          basic
++
  scalar type
  )))|(((
  Default SDMX data type
++
  (BasicComponentDataType
++
  )
  )))|Default output format
  |String|String|Like XML (xs:string)
@@ -748,15 +748,17 @@
  |Time|StandardTimePeriod|<date>/<date> (as defined above)
  |time_period|(((
  ReportingTimePeriod
++
  (StandardReportingPeriod)
  )))|(((
   YYYY-Pppp
++
  (according to SDMX )
  )))
  |Duration|Duration|Like     XML    (xs:duration) PnYnMnDTnHnMnS
  |Boolean|Boolean|Like XML (xs:boolean) with the values "true" or "false"
--**Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types**
++==== Figure 14 – Mappings from SDMX data types to VTL Basic Scalar Types ====
  In case a different default conversion is desired, it can be achieved through the CustomTypeScheme and CustomType artefacts (see also the section
@@ -814,13 +814,17 @@
  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}}.
--=== 12.4.3 Null Values ===
++1.
++11.
++111. Null Values
  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.
  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.
--=== 12.4.5 Format of the literals used in VTL Transformations ===
++1.
++11.
++111. Format of the literals used in VTL Transformations
  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.
@@ -834,6 +834,7 @@
  In case a literal is operand of a VTL Cast operation, the format specified in the Cast overrides all the possible otherwise specified formats.
++
  ----
  {{putFootnotes/}}