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1 -{{box title="**Contents**"}}
2 -{{toc/}}
3 -{{/box}}
1 +Revision History
4 4  
5 -**Revision History**
6 -
7 7  |**Revision**|**Date**|**Contents**
8 8  | |April 2011|Initial release
9 9  |1.0|April 2013|Added section 9 - Transforming between versions of SDMX
... ... @@ -13,8 +13,10 @@
13 13  
14 14  == 1.1 Purpose ==
15 15  
16 -The intention of this document is to document certain aspects of SDMX that are important to understand and will aid implementation decisions. The explanations here supplement the information documented in the SDMX XML schema and the Information Model.
12 +The intention of this document is to document certain aspects of SDMX that are important to understand and will aid implementation decisions. The explanations here supplement the information documented in the SDMX XML schema and the
17 17  
14 +Information Model.
15 +
18 18  == 1.2 Structure ==
19 19  
20 20  This document is organized into the following major parts:
... ... @@ -39,7 +39,7 @@
39 39  
40 40  == 3.2 SDMX Information Model for Format Implementers ==
41 41  
42 -=== 3.2.1 Introduction ===
40 +=== 3.2.1 Introduction ===
43 43  
44 44  The purpose of this sub-section is to provide an introduction to the SDMX-IM relating to Data Structure Definitions and Data Sets for those whose primary interest is in the use of the XML or EDI formats.  For those wishing to have a deeper understanding of the Information Model, the full SDMX-IM document, and other sections in this guide provide a more in-depth view, along with UML diagrams and supporting explanation. For those who are unfamiliar with DSDs, an appendix to the SDMX-IM provides a tutorial which may serve as a useful introduction.
45 45  
... ... @@ -47,12 +47,16 @@
47 47  
48 48  The Data Structure Definition and Data Set parts of the information model are consistent with the GESMES/TS version 3.0 Data Model (called SDMX-EDI in the SDMX standard), with these exceptions:
49 49  
50 -* the “sibling group” construct has been generalized to permit any dimension or dimensions to be wildcarded, and not just frequency, as in GESMES/TS. It has been renamed a “group” to distinguish it from the “sibling group” where only frequency is wildcarded. The set of allowable partial “group” keys must be declared in the DSD, and attributes may be attached to any of these group keys;
51 -* furthermore, whilst the “group” has been retained for compatibility with version 2.0 and with SDMX-EDI, it has, at version 2.1, been replaced by the “Attribute Relationship” definition which is explained later
52 -* the section on data representation is now a convention, to support interoperability with EDIFACT-syntax implementations ( see section 3.3.2);
48 +the “sibling group” construct has been generalized to permit any dimension or dimensions to be wildcarded, and not just frequency, as in GESMES/TS. It has been renamed a “group” to distinguish it from the “sibling group” where only frequency is wildcarded. The set of allowable partial “group” keys must be declared in the DSD, and attributes may be attached to any of these group keys;
53 53  
54 -DSD-specific data formats are derived from the model, and some supporting features for declaring multiple measures have been added to the structural metadata descriptions Clearly, this is not a coincidence. The GESMES/TS Data Model provides the foundation for the EDIFACT messages in SDMX-EDI, and also is the starting point for the development of SDMX-ML.
50 +furthermore, whilst the “group” has been retained for compatibility with version 2.0 and with SDMX-EDI, it has, at version 2.1, been replaced by the “Attribute Relationship” definition which is explained later
55 55  
52 +the section on data representation is now a convention, to support interoperability with EDIFACT-syntax implementations ( see section 3.3.2);
53 +
54 +DSD-specific data formats are derived from the model, and some supporting features for declaring multiple measures have been added to the structural metadata descriptions
55 +
56 +Clearly, this is not a coincidence. The GESMES/TS Data Model provides the foundation for the EDIFACT messages in SDMX-EDI, and also is the starting point for the development of SDMX-ML.
57 +
56 56  Note that in the descriptions below, text in courier and italicised are the names used in the information model (e.g. //DataSet//).
57 57  
58 58  == 3.3 SDMX-ML and SDMX-EDI: Comparison of Expressive Capabilities and Function ==
... ... @@ -59,16 +59,22 @@
59 59  
60 60  SDMX offers several equivalent formats for describing data and structural metadata, optimized for use in different applications. Although all of these formats are derived directly from the SDM-IM, and are thus equivalent, the syntaxes used to express the model place some restrictions on their use. Also, different optimizations provide different capabilities. This section describes these differences, and provides some rules for applications which may need to support more than one SDMX format or syntax. This section is constrained to the Data Structure Definitionand the Date Set.
61 61  
62 -=== 3.3.1 Format Optimizations and Differences ===
64 +=== 3.3.1 Format Optimizations and Differences ===
63 63  
64 64  The following section provides a brief overview of the differences between the various SDMX formats.
65 65  
66 -Version 2.0 was characterised by 4 data messages, each with a distinct format: Generic, Compact, Cross-Sectional and Utility. Because of the design, data in some formats could not always be related to another format. In version 2.1, this issue has been addressed by merging some formats and eliminating others. As a result, in SDMX 2.1 there are just two types of data formats: //GenericData// and //StructureSpecificData// (i.e. specific to one Data Structure Definition).
68 +Version 2.0 was characterised by 4 data messages, each with a distinct format: Generic, Compact, Cross-Sectional and Utility. Because of the design, data in some formats could not always be related to another format. In version 2.1, this issue has been addressed by merging some formats and eliminating others. As a result, in
67 67  
70 +SDMX 2.1 there are just two types of data formats: //GenericData// and
71 +
72 +//StructureSpecificData// (i.e. specific to one Data Structure Definition).
73 +
68 68  Both of these formats are now flexible enough to allow for data to be oriented in series with any dimension used to disambiguate the observations (as opposed to only time or a cross sectional measure in version 2.0). The formats have also been expanded to allow for ungrouped observations.
69 69  
70 -To allow for applications which only understand time series data, variations of these formats have been introduced in the form of two data messages; //GenericTimeSeriesData// and //StructureSpecificTimeSeriesData//. It is important to note that these variations are built on the same root structure and can be processed in the same manner as the base format so that they do NOT introduce additional processing requirements.
76 +To allow for applications which only understand time series data, variations of these formats have been introduced in the form of two data messages;
71 71  
78 +//GenericTimeSeriesData// and //StructureSpecificTimeSeriesData//. It is important to note that these variations are built on the same root structure and can be processed in the same manner as the base format so that they do NOT introduce additional processing requirements.
79 +
72 72  === //Structure Definition// ===
73 73  
74 74  The SDMX-ML Structure Message supports the use of annotations to the structure, which is not supported by the SDMX-EDI syntax.
... ... @@ -77,8 +77,10 @@
77 77  
78 78  === //Validation// ===
79 79  
80 -SDMX-EDI – as is typical of EDIFACT syntax messages – leaves validation to dedicated applications (“validation” being the checking of syntax, data typing, and adherence of the data message to the structure as described in the structural definition.)
88 +SDMX-EDI – as is typical of EDIFACT syntax messages – leaves validation to dedicated applications (“validation” being the checking of syntax, data typing, and adherence of the data message to the structure as described in the structural
81 81  
90 +definition.)
91 +
82 82  The SDMX-ML Generic Data Message also leaves validation above the XML syntax level to the application.
83 83  
84 84  The SDMX-ML DSD-specific messages will allow validation of XML syntax and datatyping to be performed with a generic XML parser, and enforce agreement between the structural definition and the data to a moderate degree with the same tool.
... ... @@ -89,13 +89,17 @@
89 89  
90 90  === //Character Encodings// ===
91 91  
92 -All SDMX-ML messages use the UTF-8 encoding, while SDMX-EDI uses the ISO 8879-1 character encoding. There is a greater capacity with UTF-8 to express some character sets (see the “APPENDIX: MAP OF ISO 8859-1 (UNOC) CHARACTER SET (LATIN 1 OR “WESTERN”) in the document “SYNTAX AND DOCUMENTATION VERSION 2.0”.) Many transformation tools are available which allow XML instances with UTF-8 encodings to be expressed as ISO 8879-1-encoded characters, and to transform UTF-8 into ISO 8879-1. Such tools should be used when transforming SDMX-ML messages into SDMX-EDI messages and vice-versa.
102 +All SDMX-ML messages use the UTF-8 encoding, while SDMX-EDI uses the ISO 8879-1 character encoding. There is a greater capacity with UTF-8 to express some character sets (see the “APPENDIX: MAP OF ISO 8859-1 (UNOC) CHARACTER
93 93  
104 +SET (LATIN 1 OR “WESTERN”) in the document “SYNTAX AND
105 +
106 +DOCUMENTATION VERSION 2.0”.) Many transformation tools are available which allow XML instances with UTF-8 encodings to be expressed as ISO 8879-1-encoded characters, and to transform UTF-8 into ISO 8879-1. Such tools should be used when transforming SDMX-ML messages into SDMX-EDI messages and vice-versa.
107 +
94 94  === //Data Typing// ===
95 95  
96 96  The XML syntax and EDIFACT syntax have different data-typing mechanisms. The section below provides a set of conventions to be observed when support for messages in both syntaxes is required. For more information on the SDMX-ML representations of data, see below.
97 97  
98 -==== 3.3.2 Data Types ====
112 +==== 3.3.2 Data Types ====
99 99  
100 100  The XML syntax has a very different mechanism for data-typing than the EDIFACT syntax, and this difference may create some difficulties for applications which support both EDIFACT-based and XML-based SDMX data formats. This section provides a set of conventions for the expression in data in all formats, to allow for clean interoperability between them.
101 101  
... ... @@ -111,8 +111,7 @@
111 111  1*. Maximum 70 characters.
112 112  1*. From ISO 8859-1 character set (including accented characters)
113 113  1. **Descriptions **are:
114 -1*. Maximum 350 characters;
115 -1*. From ISO 8859-1 character set.
128 +1*. Maximum 350 characters;  From ISO 8859-1 character set.
116 116  1. **Code values** are:
117 117  1*. Maximum 18 characters;
118 118  1*. Any of A..Z (upper case alphabetic), 0..9 (numeric), _ (underscore), / (solidus, slash), = (equal sign), - (hyphen);
... ... @@ -121,27 +121,24 @@
121 121  
122 122  A..Z (upper case alphabetic), 0..9 (numeric), _ (underscore)
123 123  
124 -**5. Observation values** are:
137 +1. **Observation values** are:
138 +1*. Decimal numerics (signed only if they are negative);
139 +1*. The maximum number of significant figures is:
140 +1*. 15 for a positive number
141 +1*. 14 for a positive decimal or a negative integer
142 +1*. 13 for a negative decimal
143 +1*. Scientific notation may be used.
144 +1. **Uncoded statistical concept** text values are:
145 +1*.
146 +1**. Maximum 1050 characters;
147 +1**. From ISO 8859-1 character set.
148 +1. **Time series keys**:
125 125  
126 -* Decimal numerics (signed only if they are negative);
127 -* The maximum number of significant figures is:
128 -* 15 for a positive number
129 -* 14 for a positive decimal or a negative integer
130 -* 13 for a negative decimal
131 -* Scientific notation may be used.
150 +In principle, the maximum permissible length of time series keys used in a data exchange does not need to be restricted. However, for working purposes, an effort is made to limit the maximum length to 35 characters; in this length, also (for SDMXEDI) one (separator) position is included between all successive dimension values; this means that the maximum length allowed for a pure series key (concatenation of dimension values) can be less than 35 characters.  The separator character is a colon (“:”) by conventional usage.
132 132  
133 -**6. Uncoded statistical concept** text values are:
134 -
135 -* Maximum 1050 characters;
136 -* From ISO 8859-1 character set.
137 -
138 -**7. Time series keys**:
139 -
140 -In principle, the maximum permissible length of time series keys used in a data exchange does not need to be restricted. However, for working purposes, an effort is made to limit the maximum length to 35 characters; in this length, also (for SDMXEDI) one (separator) position is included between all successive dimension values; this means that the maximum length allowed for a pure series key (concatenation of dimension values) can be less than 35 characters. The separator character is a colon (“:”) by conventional usage.
141 -
142 142  == 3.4 SDMX-ML and SDMX-EDI Best Practices ==
143 143  
144 -=== 3.4.1 Reporting and Dissemination Guidelines ===
154 +=== 3.4.1 Reporting and Dissemination Guidelines ===
145 145  
146 146  **3.4.1.1 Central Institutions and Their Role in Statistical Data Exchanges **Central institutions are the organisations to which other partner institutions "report" statistics. These statistics are used by central institutions either to compile aggregates and/or they are put together and made available in a uniform manner (e.g. on-line or on a CD-ROM or through file transfers). Therefore, central institutions receive data from other institutions and, usually, they also "disseminate" data to individual and/or institutions for end-use.  Within a country, a NSI or a national central bank (NCB) plays, of course, a central institution role as it collects data from other entities and it disseminates statistical information to end users. In SDMX the role of central institution is very important: every statistical message is based on underlying structural definitions (statistical concepts, code lists, DSDs) which have been devised by a particular agency, usually a central institution. Such an institution plays the role of the reference "structural definitions maintenance agency" for the corresponding messages which are exchanged. Of course, two institutions could exchange data using/referring to structural information devised by a third institution.
147 147  
... ... @@ -184,7 +184,7 @@
184 184  
185 185  The same code list can be used for several statistical concepts, within a data structure definition or across DSDs. Note that SDMX has recognised that these classifications are often quite large and the usage of codes in any one DSD is only a small extract of the full code list. In this version of the standard it is possible to exchange and disseminate a **partial code list** which is extracted from the full code list and which supports the dimension values valid for a particular DSD.
186 186  
187 -=== Data Structure Definition Structure ===
197 +=== Data Structure Definition Structure  ===
188 188  
189 189  The following items have to be specified by a structural definitions maintenance agency when defining a new data structure definition:
190 190  
... ... @@ -368,7 +368,7 @@
368 368  
369 369  == 4.2 Time and Time Format ==
370 370  
371 -==== 4.2.1 Introduction ====
381 +==== 4.2.1 Introduction ====
372 372  
373 373  First, it is important to recognize that most observation times are a period. SDMX specifies precisely how Time is handled.
374 374  
... ... @@ -417,7 +417,7 @@
417 417  
418 418  This is used to unambiguously state that a date-time represents an observation at a single point in time. Therefore, if one wants to use SDMX for data which is measured at a distinct point in time rather than being reported over a period, the date-time representation can be used.
419 419  
420 -Representation: xs:dateTime (YYYY-MM-DDThh:mm:ss)[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[1~]^^>>path:#_ftn1]]
430 +Representation: xs:dateTime (YYYY-MM-DDThh:mm:ss)[[^^~[1~]^^>>path:#_ftn1]]
421 421  
422 422  ==== 4.2.6 Standard Reporting Period ====
423 423  
... ... @@ -485,7 +485,7 @@
485 485  
486 486  Representation: common:ReportingWeekType (YYYY-Www, e.g. 2000-W53)
487 487  
488 -Notes: There are either 52 or 53 weeks in a reporting year. This is based on the ISO 8601 definition of a week (Monday - Saturday), where the first week of a reporting year is defined as the week with the first Thursday on or after the reporting year start day.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[2~]^^>>path:#_ftn2]](%%) The reporting week is always represented as two digits, therefore 1-9 are 0 padded (e.g. 01). This allows the values to be sorted chronologically using textual sorting methods.
498 +Notes: There are either 52 or 53 weeks in a reporting year. This is based on the ISO 8601 definition of a week (Monday - Saturday), where the first week of a reporting year is defined as the week with the first Thursday on or after the reporting year start day.[[^^~[2~]^^>>path:#_ftn2]] The reporting week is always represented as two digits, therefore 1-9 are 0 padded (e.g. 01). This allows the values to be sorted chronologically using textual sorting methods.
489 489  
490 490  **Reporting Day**:
491 491  
... ... @@ -542,7 +542,7 @@
542 542  111. If the [PERIOD_INDICATOR] is D, the [PERIOD_DURATION] is P1D.
543 543  1. **Determine [PERIOD_START]:**
544 544  
545 -Subtract one from the [PERIOD_VALUE] and multiply this by the [PERIOD_DURATION]. Add[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[3~]^^>>path:#_ftn3]](%%) this to the [REPORTING_YEAR_BASE]. The result is the [PERIOD_START].
555 +Subtract one from the [PERIOD_VALUE] and multiply this by the [PERIOD_DURATION]. Add[[^^~[3~]^^>>path:#_ftn3]] this to the [REPORTING_YEAR_BASE]. The result is the [PERIOD_START].
546 546  
547 547  1. **Determine the [PERIOD_END]:**
548 548  
... ... @@ -641,7 +641,7 @@
641 641  
642 642  When converting data from SDMX-EDI to SDMX-ML, the source time format is only necessary to determine the format of the target time value. For example, a source time format of will result in a target time in the format YYYY-Ss whereas a source format of will result in a target time value in the format YYYY-Qq.
643 643  
644 -==== 4.2.10 Time Zones ====
654 +==== 4.2.10 Time Zones ====
645 645  
646 646  In alignment with ISO 8601, SDMX allows the specification of a time zone on all time periods and on the reporting year start day. If a time zone is provided on a reporting year start day, then the same time zone (or none) should be reported for each reporting time period. If the reporting year start day and the reporting period time zone differ, the time zone of the reporting period will take precedence. Examples of each format with time zones are as follows (time zone indicated in bold):
647 647  
... ... @@ -662,7 +662,7 @@
662 662  
663 663  According to ISO 8601, a date without a time-zone is considered "local time". SDMX assumes that local time is that of the sender of the message. In this version of SDMX, an optional field is added to the sender definition in the header for specifying a time zone. This field has a default value of 'Z' (UTC). This determination of local time applies for all dates in a message.
664 664  
665 -==== 4.2.11 Representing Time Spans Elsewhere ====
675 +==== 4.2.11 Representing Time Spans Elsewhere ====
666 666  
667 667  It has been possible since SDMX 2.0 for a Component to specify a representation of a time span. Depending on the format of the data message, this resulted in either an element with 2 XML attributes for holding the start time and the duration or two separate XML attributes based on the underlying Component identifier. For example if REF_PERIOD were given a representation of time span, then in the Compact data format, it would be represented by two XML attributes; REF_PERIODStartTime (holding the start) and REF_PERIOD (holding the duration). If a new simple type is introduced in the SDMX schemas that can hold ISO 8601 time intervals, then this will no longer be necessary. What was represented as this:
668 668  
... ... @@ -672,11 +672,11 @@
672 672  
673 673  <Series REF_PERIOD="2000-01-01T00:00:00/P2M"/>
674 674  
675 -==== 4.2.12 Notes on Formats ====
685 +==== 4.2.12 Notes on Formats ====
676 676  
677 677  There is no ambiguity in these formats so that for any given value of time, the category of the period (and thus the intended time period range) is always clear. It should also be noted that by utilizing the ISO 8601 format, and a format loosely based on it for the report periods, the values of time can easily be sorted chronologically without additional parsing.
678 678  
679 -==== 4.2.13 Effect on Time Ranges ====
689 +==== 4.2.13 Effect on Time Ranges ====
680 680  
681 681  All SDMX-ML data messages are capable of functioning in a manner similar to SDMX-EDI if the Dimension at the observation level is time: the time period for the first observation can be stated and the rest of the observations can omit the time value as it can be derived from the start time and the frequency. Since the frequency can be determined based on the actual format of the time value for everything but distinct points in time and time ranges, this makes is even simpler to process as the interval between time ranges is known directly from the time value.
682 682  
... ... @@ -755,7 +755,7 @@
755 755  
756 756   2010-D185 or later (reporting year start day ~-~-07-01)
757 757  
758 -== 4.3 Structural Metadata Querying Best Practices ==
768 +== 4.3 Structural Metadata Querying Best Practices ==
759 759  
760 760  When querying for structural metadata, the ability to state how references should be resolved is quite powerful. However, this mechanism is not always necessary and can create an undue burden on the systems processing the queries if it is not used properly.
761 761  
... ... @@ -763,7 +763,7 @@
763 763  
764 764  When the referenced object is not known, then the reference resolution mechanism could be used. For example, suppose one wanted to find all category schemes and the related categorisations for a given maintenance agency. In this case, one could query for the category scheme by the maintenance agency and specify that parent and sibling references should be resolved. This would result in the categorisations which reference the categories in the matched schemes to be returned, as well as the object which they categorise.
765 765  
766 -== 4.4 Versioning and External Referencing ==
776 +== 4.4 Versioning and External Referencing ==
767 767  
768 768  Within the SDMX-ML Structure Message, there is a pattern for versioning and external referencing which should be pointed out. The identifiers are qualified by their version numbers – that is, an object with an Agency of “A”, and ID of “X” and a version of “1.0” is a different object than one with an Agency of “A’, an ID of “X”, and a version of “1.1”.
769 769  
... ... @@ -1178,12 +1178,12 @@
1178 1178  1. Restricts the code list for the CAS Dimension to codes TOT and NAP.
1179 1179  1. Inherits the AGE constraint applied at the level of the DSD.
1180 1180  
1181 -=== Provision Agreements CENSUS_CUBE1_IT ===
1191 +=== Provision Agreements CENSUS_CUBE1_IT ===
1182 1182  
1183 1183  1. Restricts the codes for the GEO Dimension to IT and its children.
1184 1184  1. Inherits the constraints from Dataflow CENSUS_CUBE1  for the AGE and CAS Dimensions.
1185 1185  
1186 -=== Provision Agreements CENSUS_CUBE2_IT ===
1196 +=== Provision Agreements CENSUS_CUBE2_IT ===
1187 1187  
1188 1188  1. Restricts the codes for the GEO Dimension to IT and its children.
1189 1189  1. Inherits the constraints from Dataflow CENSUS_CUBE2 for the CAS Dimension.
... ... @@ -1213,7 +1213,7 @@
1213 1213  
1214 1214  == 9.2 Groups and Dimension Groups ==
1215 1215  
1216 -=== 9.2.1 Issue ===
1226 +=== 9.2.1 Issue ===
1217 1217  
1218 1218  Version 2.1 introduces a more granular mechanism for specifying the relationship between a Data Attribute and the Dimensions to which the attribute applies. The technical construct for this is the Dimension Group. This Dimension Group has no direct equivalent in versions 2.0 and 1.0 and so the application transforming data from a version 2.1 data set to a version 2.0 or version 1.0 data set must decide to which construct the attribute value, whose Attribute is declared in a Dimension Group, should be attached. The closest construct is the “Series” attachment level and in many cases this is the correct construct to use.
1219 1219  
... ... @@ -1238,7 +1238,7 @@
1238 1238  
1239 1239  == 10.1 Introduction ==
1240 1240  
1241 -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" %)^^~[4~]^^>>path:#_ftn4]](%%). The purpose of the VTL in the SDMX context is to enable the:
1251 +The Validation and Transformation Language (VTL) supports the definition of Transformations, which are algorithms to calculate new data starting from already existing ones[[^^~[4~]^^>>path:#_ftn4]]. The purpose of the VTL in the SDMX context is to enable the:
1242 1242  
1243 1243  * definition of validation and transformation algorithms, in order to specify how to calculate new data  from existing ones;
1244 1244  * 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);
... ... @@ -1252,7 +1252,7 @@
1252 1252  
1253 1253  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.
1254 1254  
1255 -== 10.2 References to SDMX artefacts from VTL statements ==
1265 +== 10.2 References to SDMX artefacts from VTL statements ==
1256 1256  
1257 1257  === 10.2.1 Introduction ===
1258 1258  
... ... @@ -1262,7 +1262,7 @@
1262 1262  
1263 1263  In any case, the aliases used in the VTL transformations have to be mapped to the
1264 1264  
1265 -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" %)^^~[5~]^^>>path:#_ftn5]](%%) or user defined operators[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[6~]^^>>path:#_ftn6]](%%)  to reference SDMX artefacts. A VtlMappingScheme is a container for zero or more VtlMapping. 
1275 +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[[^^~[5~]^^>>path:#_ftn5]] or user defined operators[[^^~[6~]^^>>path:#_ftn6]]  to reference SDMX artefacts. A VtlMappingScheme is a container for zero or more VtlMapping. 
1266 1266  
1267 1267  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.
1268 1268  
... ... @@ -1272,15 +1272,15 @@
1272 1272  
1273 1273  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.
1274 1274  
1275 -The SDMX URN[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[7~]^^>>path:#_ftn7]](%%) is the concatenation of the following parts, separated by special symbols like dot, equal, asterisk, comma, and parenthesis:^^ ^^
1285 +The SDMX URN[[^^~[7~]^^>>path:#_ftn7]] is the concatenation of the following parts, separated by special symbols like dot, equal, asterisk, comma, and parenthesis:^^ ^^
1276 1276  
1277 -* SDMXprefix                                                                                   
1278 -* SDMX-IM-package-name             
1279 -* class-name                                                                        
1280 -* agency-id                                                                          
1287 +* SDMXprefix
1288 +* SDMX-IM-package-name 
1289 +* class-name
1290 +* agency-id 
1281 1281  * maintainedobject-id
1282 1282  * maintainedobject-version
1283 -* container-object-id [[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[8~]^^>>path:#_ftn8]]
1293 +* container-object-id [[^^~[8~]^^>>path:#_ftn8]]
1284 1284  * object-id
1285 1285  
1286 1286  The generic structure of the URN is the following:
... ... @@ -1299,7 +1299,7 @@
1299 1299  
1300 1300  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).
1301 1301  
1302 -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" %)^^~[9~]^^>>path:#_ftn9]](%%), coincides with the name of the artefact. Therefore the maintainedobject-id depends on the class of the artefact:
1312 +The **maintainedobject-id** is the name of the maintained object which the artefact belongs to, and in case the artefact itself is maintainable[[^^~[9~]^^>>path:#_ftn9]], coincides with the name of the artefact. Therefore the maintainedobject-id depends on the class of the artefact:
1303 1303  
1304 1304  * if the artefact is a ,,Dataflow,,, which is a maintainable class,  the maintainedobject-id is the Dataflow name (dataflow-id);
1305 1305  * if the artefact is a Dimension, MeasureDimension, TimeDimension, PrimaryMeasure or DataAttribute, which are not maintainable and belong to the ,,DataStructure,, maintainable class, the maintainedobject-id is the name of the DataStructure (dataStructure-id) which the artefact belongs to;
... ... @@ -1319,7 +1319,7 @@
1319 1319  
1320 1320  * if the artefact is a ,,Concept ,,(the object-id is the name of the ,,Concept,,)
1321 1321  
1322 -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 and their Agency is AG, would be written as[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[10~]^^>>path:#_ftn10]](%%):
1332 +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 and their Agency is AG, would be written as[[^^~[10~]^^>>path:#_ftn10]]:
1323 1323  
1324 1324  ‘urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DFR(1.0)’  <-
1325 1325  
... ... @@ -1335,10 +1335,10 @@
1335 1335  
1336 1336  * 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.
1337 1337  * 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: 
1338 -** “datastructure” for the classes Dataflow, Dimension, MeasureDimension, TimeDimension, PrimaryMeasure, DataAttribute,  
1348 +** “datastructure” for the classes Dataflow, Dimension, MeasureDimension, TimeDimension, PrimaryMeasure, DataAttribute,
1339 1339  ** “conceptscheme” for the classes Concept and ConceptScheme o “codelist” for the class Codelist.
1340 -* 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" %)^^~[11~]^^>>path:#_ftn11]](%%), 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" %)^^~[12~]^^>>path:#_ftn12]](%%).
1341 -* 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 agency-id can be omitted if it is the same as the invoking T,,ransformationScheme,, and cannot be omitted if the artefact comes from another agency.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[13~]^^>>path:#_ftn13]](%%)  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).
1350 +* 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[[^^~[11~]^^>>path:#_ftn11]], the SDMX class can be deduced from the mapping rules between VTL and SDMX (see the section “Mapping between VTL and SDMX” hereinafter)[[^^~[12~]^^>>path:#_ftn12]].
1351 +* 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 agency-id can be omitted if it is the same as the invoking T,,ransformationScheme,, and cannot be omitted if the artefact comes from another agency.[[^^~[13~]^^>>path:#_ftn13]]  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).
1342 1342  * 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;
1343 1343  ** if the referenced artefact is a Dimension, MeasureDimension, TimeDimension, PrimaryMeasure, DataAttribute, which are not maintainable and belong to the ,,DataStructure,, maintainable class, the maintainedobject-id is the dataStructure-id and can be omitted, given that these components are always invoked within the invocation of a ,,Dataflow,,, whose dataStructure-id can be deduced from the
1344 1344  
... ... @@ -1349,7 +1349,7 @@
1349 1349  ** if the referenced artefact is a ,,Codelist, ,,which is a maintainable class, the maintainedobject-id is the ,,codelist-id,, and obviously cannot be omitted.
1350 1350  * 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.,, ,,
1351 1351  * As said, the **container-object-id** does not apply to the classes that can be referenced in VTL transformations, therefore is not present in their URN
1352 -* The **object-id** does not exist for the artefacts belonging to the ,,Dataflow, ConceptScheme,, and ,,Codelist,, classes, while it exists and cannot be omitted for the artefacts belonging to the classes Dimension, MeasureDimension, TimeDimension, PrimaryMeasure, DataAttribute and Concept, as for
1362 +* The **object-id** does not exist for the artefacts belonging to the ,,Dataflow,,,,, ConceptScheme,, and ,,Codelist,, classes, while it exists and cannot be omitted for the artefacts belonging to the classes Dimension, MeasureDimension, TimeDimension, PrimaryMeasure, DataAttribute and Concept, as for
1353 1353  
1354 1354  them the object-id is the main identifier of the artefact
1355 1355  
... ... @@ -1361,15 +1361,15 @@
1361 1361  
1362 1362  ‘urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=AG:DF2(1.0)’
1363 1363  
1364 -by omitting all the non-essential parts would become simply:                          
1374 +by omitting all the non-essential parts would become simply:  
1365 1365  
1366 1366  DFR  :=  DF1 + DF2
1367 1367  
1368 -The references to the ,,Codelists,, can be simplified similarly. For example, given the non-abbreviated reference to the ,,Codelist,,  AG:CL_FREQ(1.0), which is[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[14~]^^>>path:#_ftn14]](%%):
1378 +The references to the ,,Codelists,, can be simplified similarly. For example, given the non-abbreviated reference to the ,,Codelist,,  AG:CL_FREQ(1.0), which is[[^^~[14~]^^>>path:#_ftn14]]:
1369 1369  
1370 1370  ‘urn:sdmx:org.sdmx.infomodel.codelist.Codelist=AG:CL_FREQ(1.0)’
1371 1371  
1372 -if the ,,Codelist,, is referenced from a ruleset scheme belonging to the agency AG, omitting all the optional parts, the abbreviated reference would become simply[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[15~]^^>>path:#_ftn15]](%%):
1382 +if the ,,Codelist,, is referenced from a ruleset scheme belonging to the agency AG, omitting all the optional parts, the abbreviated reference would become simply[[^^~[15~]^^>>path:#_ftn15]]:
1373 1373  
1374 1374  CL_FREQ
1375 1375  
... ... @@ -1379,7 +1379,7 @@
1379 1379  
1380 1380  SECTOR
1381 1381  
1382 -For example, the transformation for renaming the component SECTOR of the dataflow DF1 into SEC can be written as[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[16~]^^>>path:#_ftn16]](%%):
1392 +For example, the transformation for renaming the component SECTOR of the dataflow DF1 into SEC can be written as[[^^~[16~]^^>>path:#_ftn16]]:
1383 1383  
1384 1384  ‘DFR(1.0)’ := ‘DF1(1.0)’ [rename SECTOR to SEC]
1385 1385  
... ... @@ -1413,9 +1413,9 @@
1413 1413  
1414 1414  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. 
1415 1415  
1416 -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 or to a SDMX ConceptScheme (for SDMX measure dimensions), 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" %)^^~[17~]^^>>path:#_ftn17]](%%).
1426 +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 or to a SDMX ConceptScheme (for SDMX measure dimensions), while a reference to a VTL Represented Variable becomes a reference to a SDMX Concept, assuming for it a definite representation[[^^~[17~]^^>>path:#_ftn17]].
1417 1417  
1418 -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" %)^^~[18~]^^>>path:#_ftn18]](%%)
1428 +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.[[^^~[18~]^^>>path:#_ftn18]]
1419 1419  
1420 1420  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, ConceptScheme, Concept) to can be deduced from the Ruleset signature.
1421 1421  
... ... @@ -1429,15 +1429,15 @@
1429 1429  
1430 1430  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. 
1431 1431  
1432 -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" %)^^~[19~]^^>>path:#_ftn19]](%%).
1442 +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[[^^~[19~]^^>>path:#_ftn19]].
1433 1433  
1434 1434  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 assignmentStatus 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). 
1435 1435  
1436 1436  === 10.3.2 General mapping of VTL and SDMX data structures ===
1437 1437  
1438 -This section makes reference to the VTL “Model for data and their structure”[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[20~]^^>>path:#_ftn20]](%%) and the correspondent SDMX “Data Structure Definition”[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[21~]^^>>path:#_ftn21]](%%).
1448 +This section makes reference to the VTL “Model for data and their structure”[[^^~[20~]^^>>path:#_ftn20]] and the correspondent SDMX “Data Structure Definition”[[^^~[21~]^^>>path:#_ftn21]].
1439 1439  
1440 -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).[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[22~]^^>>path:#_ftn22]](%%)
1450 +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).[[^^~[22~]^^>>path:#_ftn22]]
1441 1441  
1442 1442  While the VTL Transformations are defined in term of Dataflow definitions, they are assumed to be executed on instances of such Dataflows, provided at runtime to the VTL engine (the mechanism for identifying the instances to be processed are not part of the VTL specifications and depend on the implementation of the VTL-based systems).  As already said, the SDMX Datasets are instances of SDMX Dataflows, therefore a VTL Transformation defined on some SDMX Dataflows can be applied on some corresponding SDMX Datasets.
1443 1443  
... ... @@ -1447,7 +1447,7 @@
1447 1447  
1448 1448  SDMX DimensionComponent can be a Dimension, a TimeDimension or a MeasureDimension. Correspondingly, in the SDMX implementation of the VTL, the VTL Identifiers can be (optionally) distinguished in three sub-classes (Simple Identifier, Time Identifier, Measure Identifier) even if such a distinction is not evidenced in the VTL IM. 
1449 1449  
1450 -However, a VTL Data Structure can have any number of Identifiers, Measures and Attributes, while a SDMX 2.1 DataStructureDefinition can have any number of Dimensions and DataAttributes but just one PrimaryMeasure[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[23~]^^>>path:#_ftn23]](%%). This is due to a difference between SDMX 2.1 and VTL in the possible representation methods of the data that contain more measures.
1460 +However, a VTL Data Structure can have any number of Identifiers, Measures and Attributes, while a SDMX 2.1 DataStructureDefinition can have any number of Dimensions and DataAttributes but just one PrimaryMeasure[[^^~[23~]^^>>path:#_ftn23]]. This is due to a difference between SDMX 2.1 and VTL in the possible representation methods of the data that contain more measures.
1451 1451  
1452 1452  As for SDMX, because the data structure cannot contain more than one measure component (i.e., the primaryMeasure), the representation of data having more measures is possible only by means of a particular dimension, called MeasureDimension, which is aimed at containing the name of the measure concepts, so that for each observation the value contained in the PrimaryMeasure component is the value of the measure concept reported in the MeasureDimension component. 
1453 1453  
... ... @@ -1537,7 +1537,7 @@
1537 1537  
1538 1538  This mapping method cannot be applied for SDMX 2.1 if the VTL data structure has more than one measure component, given that the SDMX 2.1 DataStructureDefinition allows just one measure component (the
1539 1539  
1540 -PrimaryMeasure). In this case it becomes mandatory to specify a different 1958 mapping method through the VtlMappingScheme and VtlDataflowMapping 1959 classes.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[24~]^^>>path:#_ftn24]](%%)
1550 +PrimaryMeasure). In this case it becomes mandatory to specify a different 1958 mapping method through the VtlMappingScheme and VtlDataflowMapping 1959 classes.[[^^~[24~]^^>>path:#_ftn24]]
1541 1541  
1542 1542  1960 Please note that the VTL measures can have any name while in SDMX 2.1 the 1961 MeasureComponent has the mandatory name “obs_value”, therefore the name of the VTL measure name must become “obs_value” in SDMX 2.1. 
1543 1543  
... ... @@ -1654,15 +1654,15 @@
1654 1654  
1655 1655   The VtlMappingScheme is a container for zero or more VtlDataflowMapping (besides possible mappings to artefacts other than dataflows).
1656 1656  
1657 -=== 10.3.6 Mapping dataflow subsets to distinct VTL data sets[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^**~[25~]**^^>>path:#_ftn25]](%%) ===
1667 +=== 10.3.6 Mapping dataflow subsets to distinct VTL data sets[[^^**~[25~]**^^>>path:#_ftn25]] ===
1658 1658  
1659 1659  Until now it as been assumed to map one SMDX Dataflow to one VTL dataset 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
1660 1660  
1661 1661  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).
1662 1662  
1663 -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.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[26~]^^>>path:#_ftn26]](%%)
1673 +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.[[^^~[26~]^^>>path:#_ftn26]]
1664 1664  
1665 -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.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[27~]^^>>path:#_ftn27]](%%)
1675 +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.[[^^~[27~]^^>>path:#_ftn27]]
1666 1666  
1667 1667   Given a SDMX Dataflow and some predefined Dimensions of its
1668 1668  
... ... @@ -1674,14 +1674,14 @@
1674 1674  
1675 1675  In practice, this kind mapping is obtained like follows:
1676 1676  
1677 -* For a given SDMX dataflow, the user (VTL definer) declares  the dimension components on which the mapping will be based, in a given order.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[28~]^^>>path:#_ftn28]](%%) Following the example above, imagine that the user declares the dimensions INDICATOR and COUNTRY.
1687 +* For a given SDMX dataflow, the user (VTL definer) declares  the dimension components on which the mapping will be based, in a given order.[[^^~[28~]^^>>path:#_ftn28]] Following the example above, imagine that the user declares the dimensions INDICATOR and COUNTRY.
1678 1678  * The VTL dataset is given a name using a special notation also called “ordered concatenation” and composed of the following parts: 
1679 1679  ** The reference to the SDMX dataflow (expressed according to the rules described in the previous paragraphs, i.e. URN, abbreviated
1680 1680  
1681 -URN or another alias); for example DF(1.0); o a slash (“/”) as a separator; [[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[29~]^^>>path:#_ftn29]]
1691 +URN or another alias); for example DF(1.0); o a slash (“/”) as a separator; [[^^~[29~]^^>>path:#_ftn29]]
1682 1682  
1683 1683  *
1684 -** The reference to a specific part of the SDMX dataflow above, expressed as the concatenation of the values that the SDMX dimensions declared above must have, separated by dots (“.”) and written in the order in which these dimensions are defined[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[30~]^^>>path:#_ftn30]](%%) . For example  POPULATION.USA would mean that such a VTL dataset is mapped to the SDMX observations for which the dimension  //INDICATOR// is equal to POPULATION and the dimension //COUNTRY// is equal to USA.
1694 +** The reference to a specific part of the SDMX dataflow above, expressed as the concatenation of the values that the SDMX dimensions declared above must have, separated by dots (“.”) and written in the order in which these dimensions are defined[[^^~[30~]^^>>path:#_ftn30]] . For example  POPULATION.USA would mean that such a VTL dataset is mapped to the SDMX observations for which the dimension  //INDICATOR// is equal to POPULATION and the dimension //COUNTRY// is equal to USA.
1685 1685  
1686 1686  In the VTL transformations, this kind of dataset name must be referenced between single quotes because the slash (“/”) is not a regular character according to the VTL rules.
1687 1687  
... ... @@ -1699,7 +1699,7 @@
1699 1699  
1700 1700  Let us now analyse the different meaning of this kind of mapping in the two mapping directions, i.e. from SDMX to VTL and from VTL to SDMX.
1701 1701  
1702 -As already said, the mapping from SDMX to VTL happens when the VTL datasets are operand of VTL transformations, instead the mapping from VTL to SDMX happens when the VTL datasets are result of VTL transformations[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[31~]^^>>path:#_ftn31]](%%) and need to be treated as SDMX objects. This kind of mapping can be applied independently in the two directions and the Dimensions on which the mapping is based can be different in the two directions: these Dimensions are defined in the ToVtlSpaceKey and in the FromVtlSpaceKey classes respectively.
1712 +As already said, the mapping from SDMX to VTL happens when the VTL datasets are operand of VTL transformations, instead the mapping from VTL to SDMX happens when the VTL datasets are result of VTL transformations[[^^~[31~]^^>>path:#_ftn31]] and need to be treated as SDMX objects. This kind of mapping can be applied independently in the two directions and the Dimensions on which the mapping is based can be different in the two directions: these Dimensions are defined in the ToVtlSpaceKey and in the FromVtlSpaceKey classes respectively.
1703 1703  
1704 1704  First, let us see what happens in the mapping direction from SDMX to VTL, i.e. when parts of a SDMX dataflow (e.g. DF1(1.0)) need to be mapped to distinct VTL datasets that are operand of some VTL transformations.
1705 1705  
... ... @@ -1709,7 +1709,7 @@
1709 1709  
1710 1710  //COUNTRYvalue//. For example, the VTL dataset ‘DF1(1.0)/POPULATION.USA’ would contain all the observations of DF1(1.0) having INDICATOR = POPULATION and COUNTRY = USA.
1711 1711  
1712 -In order to obtain the data structure of these VTL datasets from the SDMX one, it is assumed that the SDMX dimensions on which the mapping is based are dropped, i.e. not maintained in the VTL data structure; this is possible because their values are fixed for each one of the invoked VTL datasets[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[32~]^^>>path:#_ftn32]](%%). After that, the mapping method from SDMX to VTL specified for the dataflow DF1(1.0) is applied (i.e. basic, pivot …). 
1722 +In order to obtain the data structure of these VTL datasets from the SDMX one, it is assumed that the SDMX dimensions on which the mapping is based are dropped, i.e. not maintained in the VTL data structure; this is possible because their values are fixed for each one of the invoked VTL datasets[[^^~[32~]^^>>path:#_ftn32]]. After that, the mapping method from SDMX to VTL specified for the dataflow DF1(1.0) is applied (i.e. basic, pivot …). 
1713 1713  
1714 1714  In the example above, for all the datasets of the kind
1715 1715  
... ... @@ -1729,7 +1729,7 @@
1729 1729  
1730 1730  …   …   …
1731 1731  
1732 -In fact the VTL operator “sub” has exactly the same behaviour. Therefore, mapping different parts of a SDMX dataflow to different VTL datasets in the direction from SDMX to VTL through the ordered concatenation notation is equivalent to a proper use of the operator “**sub**” on such a dataflow. [[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[33~]^^>>path:#_ftn33]]
1742 +In fact the VTL operator “sub” has exactly the same behaviour. Therefore, mapping different parts of a SDMX dataflow to different VTL datasets in the direction from SDMX to VTL through the ordered concatenation notation is equivalent to a proper use of the operator “**sub**” on such a dataflow. [[^^~[33~]^^>>path:#_ftn33]]
1733 1733  
1734 1734  In the direction from SDMX to VTL it is allowed to omit the value of one or more Dimensions on which the mapping is based, but maintaining all the separating dots (therefore it may happen to find two or more consecutive dots and dots in the beginning or in the end). The absence of value means that for the corresponding Dimension all the values are kept and the Dimension is not dropped.
1735 1735  
... ... @@ -1752,12 +1752,12 @@
1752 1752  
1753 1753  For example, let us assume that the VTL programmer wants to calculate the SDMX dataflow DF2(1.0) having the Dimensions TIME_PERIOD, INDICATOR, and COUNTRY and that such a programmer finds it convenient to calculate separately the parts of DF2(1.0) that have different combinations of values for INDICATOR and COUNTRY:
1754 1754  
1755 -* each part is calculated as a  VTL derived dataset, result of a dedicated VTL transformation; [[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[34~]^^>>path:#_ftn34]](%%)
1756 -* the data structure of all these VTL datasets has the TIME_PERIOD identifier and does not have the INDICATOR and COUNTRY identifiers.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[35~]^^>>path:#_ftn35]]
1765 +* each part is calculated as a  VTL derived dataset, result of a dedicated VTL transformation; [[^^~[34~]^^>>path:#_ftn34]]
1766 +* the data structure of all these VTL datasets has the TIME_PERIOD identifier and does not have the INDICATOR and COUNTRY identifiers.[[^^~[35~]^^>>path:#_ftn35]]
1757 1757  
1758 -Under these hypothesis, such derived VTL datasets can be mapped to DF2(1.0) by declaring the Dimensions INDICATOR and COUNTRY as mapping dimensions[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[36~]^^>>path:#_ftn36]](%%).
1768 +Under these hypothesis, such derived VTL datasets can be mapped to DF2(1.0) by declaring the Dimensions INDICATOR and COUNTRY as mapping dimensions[[^^~[36~]^^>>path:#_ftn36]].
1759 1759  
1760 -The corresponding VTL transformations, assuming that the result needs to be persistent, would be of this kind:^^ ^^[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[37~]^^>>path:#_ftn37]]
1770 +The corresponding VTL transformations, assuming that the result needs to be persistent, would be of this kind:^^ ^^[[^^~[37~]^^>>path:#_ftn37]]
1761 1761  
1762 1762  ‘DF2(1.0)///INDICATORvalue//.//COUNTRYvalue//’  <-  expression
1763 1763  
... ... @@ -1779,19 +1779,19 @@
1779 1779  As said, it is assumed that these VTL derived datasets 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:
1780 1780  
1781 1781  |(((
1782 - //VTL dataset                                             //
1792 + //VTL dataset //
1783 1783  
1784 1784  
1785 1785  )))|(% colspan="2" %)//INDICATOR value //|(% colspan="2" %)//COUNTRY value//
1786 -|‘DF2(1.0)/GDPPERCAPITA.USA’              |GDPPERCAPITA| | |USA
1796 +|‘DF2(1.0)/GDPPERCAPITA.USA’    |GDPPERCAPITA| | |USA
1787 1787  |(((
1788 1788  ‘DF2(1.0)/GDPPERCAPITA.CANADA’  
1789 1789  
1790 1790  …   …   …
1791 1791  )))|GDPPERCAPITA| | |CANADA
1792 -|‘DF2(1.0)/POPGROWTH.USA’                  |POPGROWTH | | |USA
1802 +|‘DF2(1.0)/POPGROWTH.USA’   |POPGROWTH | | |USA
1793 1793  |(((
1794 -‘DF2(1.0)/POPGROWTH.CANADA’         
1804 +‘DF2(1.0)/POPGROWTH.CANADA’   
1795 1795  
1796 1796  …   …   …
1797 1797  )))|POPGROWTH | | |CANADA 
... ... @@ -1824,9 +1824,9 @@
1824 1824  
1825 1825  …);
1826 1826  
1827 -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)[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[38~]^^>>path:#_ftn38]](%%), which can be mapped one-to-one to the homonymous SDMX dataflow having the dimension components TIME_PERIOD, INDICATOR and COUNTRY.
1837 +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)[[^^~[38~]^^>>path:#_ftn38]], which can be mapped one-to-one to the homonymous SDMX dataflow having the dimension components TIME_PERIOD, INDICATOR and COUNTRY.
1828 1828  
1829 -Therefore, mapping different VTL datasets having the same data structure to different parts of a SDMX dataflow, i.e. in the direction from VTL to SDMX, through the ordered concatenation notation is equivalent to a proper use of the operators “calc” and “union” on such datasets. [[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[39~]^^>>path:#_ftn39]](%%)[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[40~]^^>>path:#_ftn40]]
1839 +Therefore, mapping different VTL datasets having the same data structure to different parts of a SDMX dataflow, i.e. in the direction from VTL to SDMX, through the ordered concatenation notation is equivalent to a proper use of the operators “calc” and “union” on such datasets. [[^^~[39~]^^>>path:#_ftn39]][[^^~[40~]^^>>path:#_ftn40]]
1830 1830  
1831 1831  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).
1832 1832  
... ... @@ -1849,7 +1849,7 @@
1849 1849  )))
1850 1850  |**Code**|**Code** (for enumerated Dimension, PrimaryMeasure, DataAttribute) or **Concept** (for MeasureDimension)
1851 1851  |**Described Value Domain**|(((
1852 -non-enumerated** Representation**
1862 +non-enumerated** Representation**
1853 1853  
1854 1854  (having Facets / ExtendedFacets, see the Structure Pattern in the Base Package)
1855 1855  )))
... ... @@ -1875,7 +1875,7 @@
1875 1875  
1876 1876  Domain) is not identifiable. As a consequence, the definition of the VTL rulesets, which in VTL can refer either to enumerated or non-enumerated value domains, in SDMX can refer only to enumerated Value Domains (i.e. to SDMX Codelists). 
1877 1877  
1878 -As for the mapping between VTL variables and SDMX Concepts, it should be noted that these artefacts do not coincide perfectly. In fact, the VTL variables are  represented variables, defined always on the same Value Domain (“Representation” in SDMX) independently of the data set / data structure in which they appear[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[41~]^^>>path:#_ftn41]](%%), while the SDMX Concepts can have different Representations in different DataStructures.[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[42~]^^>>path:#_ftn42]](%%) This means that one SDMX Concept can correspond to many VTL Variables, one for each representation the Concept has.
1888 +As for the mapping between VTL variables and SDMX Concepts, it should be noted that these artefacts do not coincide perfectly. In fact, the VTL variables are  represented variables, defined always on the same Value Domain (“Representation” in SDMX) independently of the data set / data structure in which they appear[[^^~[41~]^^>>path:#_ftn41]], while the SDMX Concepts can have different Representations in different DataStructures.[[^^~[42~]^^>>path:#_ftn42]] This means that one SDMX Concept can correspond to many VTL Variables, one for each representation the Concept has.
1879 1879  
1880 1880  Therefore, it is important to be aware that some VTL operations (for example the binary operations at data set level) are consistent only if the components having the same names in the operated VTL data sets have also the same representation (i.e. the same Value Domain as for VTL).   For example, it is possible to obtain correct results from the VTL expression
1881 1881  
... ... @@ -1924,7 +1924,7 @@
1924 1924  
1925 1925  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.
1926 1926  
1927 -=== 10.4.3 Mapping SDMX data types to VTL basic scalar types ===
1937 +=== 10.4.3 Mapping SDMX data types to VTL basic scalar types ===
1928 1928  
1929 1929  The following table describes the default mapping for converting from the SDMX data types to the VTL basic scalar types.
1930 1930  
... ... @@ -1991,7 +1991,7 @@
1991 1991  |(((
1992 1992  **Boolean **
1993 1993  
1994 -(corresponds to the XML Schema xs:boolean datatype; support the mathematical concept of binary-valued logic: {true, false}) 
2004 +(corresponds to the XML Schema xs:boolean datatype; support the mathematical concept of binary-valued logic: {true, false})
1995 1995  )))|**boolean**
1996 1996  |(((
1997 1997  **URI **
... ... @@ -2134,7 +2134,7 @@
2134 2134  
2135 2135  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).
2136 2136  
2137 -=== 10.4.4 Mapping VTL basic scalar types to SDMX data types ===
2147 +=== 10.4.4 Mapping VTL basic scalar types to SDMX data types ===
2138 2138  
2139 2139  The following table describes the default conversion from the VTL basic scalar types to the SDMX data types .
2140 2140  
... ... @@ -2220,7 +2220,7 @@
2220 2220  |N|fixed number of digits used in the preceding  textual representation of the month or the day
2221 2221  | |
2222 2222  
2223 -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[[(% class="wikiinternallink wikiinternallink wikiinternallink wikiinternallink" %)^^~[43~]^^>>path:#_ftn43]](%%).
2233 +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[[^^~[43~]^^>>path:#_ftn43]].
2224 2224  
2225 2225  === 10.4.5 Null Values ===
2226 2226