Changes for page SDMX 2.1 Standards. Section 1. Framework for SDMX technical standards

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  |(% style="width:154px" %) |(% style="width:118px" %)April 2011|(% style="width:533px" %)Initial release
  |(% style="width:154px" %)1.0|(% style="width:118px" %)July 2020|(% style="width:533px" %)(((
  Added the last two sentences of the Section 1 – Introduction
--Added the Section 10 –Validation and Transformation Language (VTL)
++Added the Section 10 –Validation and Transformation Language (VTL(% style="background-color:transparent" %))
  )))
--(((
  = {{id name="_Toc38908"/}}1. Introduction =
--)))
--The Statistical Data and Metadata Exchange (SDMX) initiative (http:~/~/www.sdmx.org) sets standards that can facilitate the exchange of statistical data and metadata using modern information technology, with an emphasis on aggregated data.
++The [[Statistical Data and Metadata Exchange>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] ([[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]) initiative (http:~/~/www.[[sdmx>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]].org) sets standards that can facilitate the exchange of statistical data and metadata using modern information technology, with an emphasis on aggregated data.
--There are several sections to the SDMX Technical Specification:
++There are several sections to the [[SDMX Technical Specification>>doc:sdmx:Glossary.SDMX Technical Specification.WebHome]]:
--1. SDMX Framework Document – this document. The purpose of this document is to introduce SDMX and its scope. This document will be revised in due course to include the conformance requirements.
--1. The SDMX Information Model - the information model on which syntaxspecific implementations described in the other sections are based. This is intended for technicians wishing to understand the complete scope of the technical standards in a syntax-neutral form. It includes as an annex a tutorial on UML (Unified Modelling Language). This document is not normative.
--1. SDMX-EDI - the UN/EDIFACT format for exchange of SDMX-structured data and metadata. This document contains normative sections describing the use of the UN/EDIFACT syntax in SDMX messages. This document has normative sections.
--1. SDMX-ML - the XML format for the exchange of SDMX-structured data and metadata. This document has normative sections describing the use of the XML syntax in SDMX messages, and is accompanied by a set of normative XML schemas and non-normative sample XML document instances.
--1. The SDMX Registry Specification provides for a central registry of information about available data and reference metadata, and for a repository containing structural metadata and provisioning information. This specification defines the basic services offered by the SDMX Registry: registration of data and metadata; querying for data and metadata; and subscription/notification regarding updates to the registry. This document has normative sections.
--1. The SDMX Technical Notes – this is a guide to help those who wish to use the SDMX specifications. It includes notes on the expressive differences of the various messages and syntaxes; versioning; maintenance agencies; the SDMX Registry. This document is not normative.
--1. Web Services Guidelines – this is a guide for those who wish to implement SDMX using web-services technologies. It places an emphasis on those aspects of web-services technologies (including, but not requiring, an SDMXconformant registry) which will work regardless of the development environment or platform used to create the web services. This document contains normative sections.^^[[(% class="wikiinternallink wikiinternallink" %)^^1^^>>path:#sdfootnote1sym||name="sdfootnote1anc"]](%%)^^
++1. [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Framework Document – this document. The purpose of this document is to introduce [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] and its scope. This document will be revised in due course to include the conformance requirements.
++1. The [[SDMX Information Model>>doc:sdmx:Glossary.SDMX Information Model.WebHome]] - the information model on which syntaxspecific implementations described in the other sections are based. This is intended for technicians wishing to understand the complete scope of the technical standards in a syntax-neutral form. It includes as an annex a tutorial on UML (Unified Modelling Language). This document is not normative.
++1. [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]-EDI - the UN/EDIFACT format for exchange of [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]-structured data and metadata. This document contains normative sections describing the use of the UN/EDIFACT syntax in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] messages. This document has normative sections.
++1. [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]-ML - the XML format for the exchange of [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]]-structured data and metadata. This document has normative sections describing the use of the XML syntax in [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] messages, and is accompanied by a set of normative XML schemas and non-normative sample XML document instances.
++1. The [[SDMX Registry>>doc:sdmx:Glossary.SDMX Registry.WebHome]] Specification provides for a central registry of information about available data and [[reference metadata>>doc:sdmx:Glossary.Reference metadata.WebHome]], and for a repository containing [[structural metadata>>doc:sdmx:Glossary.Structural metadata.WebHome]] and provisioning information. This specification defines the basic services offered by the [[SDMX Registry>>doc:sdmx:Glossary.SDMX Registry.WebHome]]: registration of data and metadata; querying for data and metadata; and [[subscription>>doc:sdmx:Glossary.Subscription.WebHome]]/[[notification>>doc:sdmx:Glossary.Notification.WebHome]] regarding updates to the registry. This document has normative sections.
++1. The [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] Technical Notes – this is a guide to help those who wish to use the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] specifications. It includes notes on the expressive differences of the various messages and syntaxes; versioning; [[maintenance agencies>>doc:sdmx:Glossary.Maintenance agency.WebHome]]; the [[SDMX Registry>>doc:sdmx:Glossary.SDMX Registry.WebHome]]. This document is not normative.
++1. Web Services Guidelines – this is a guide for those who wish to implement [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] using web-services technologies. It places an emphasis on those aspects of web-services technologies (including, but not requiring, an SDMXconformant registry) which will work regardless of the development environment or platform used to create the web services. This document contains normative sections.{{footnote}}SOAP and REST specifications are not maintained any more in this section, see the SDMX website.{{/footnote}}
--In July 2020 it was released an important improvement of the SDMX 2.1 specifications for the SDMX implementation of the Validation and Transformation Language (VTL). This implied a revision of some of the SDMX 2.1 sections. The relevant changes are not described in the next section but in the section 10 below.
++In July 2020 it was released an important improvement of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 specifications for the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] implementation of the [[Validation and Transformation Language>>doc:sdmx:Glossary.Validation and transformation language.WebHome]] ([[VTL>>doc:sdmx:Glossary.Validation and transformation language.WebHome]]). This implied a revision of some of the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] 2.1 sections. The relevant changes are not described in the next section but in the section 10 below.
--Please note also that the SOAP and REST specifications are not maintained any more in the section 7 (Web Service Guidelines), the link to these specifications can be found on the SDMX website
++Please note also that the SOAP and REST specifications are not maintained any more in the section 7 (Web Service Guidelines), the link to these specifications can be found on the [[SDMX>>doc:sdmx:Glossary.Statistical data and metadata exchange.WebHome]] website
--1. (((
  = {{id name="_Toc38909"/}}2. Changes from Previous Version =
--)))
  The 2.0 version of this standard represented a significant increase in scope, and also provided more complete support in those areas covered in the version 1.0 specification. Version 2.0 of this standard is backward-compatible with version 1.0, so that existing implementations can be easily migrated to conformance with version 2.0.
@@ -46,45 +46,25 @@
  * **Reference Metadata**: In addition to describing and specifying data structures and formats (along with related structural metadata), the version 2.0 specification also provides for the exchange of metadata which is distinct from the structural metadata in the 1.0 version. This category includes “reference” metadata (regarding data quality, methodology, and similar types – it can be configured by the user to include whatever concepts require reporting); metadata related to data provisioning (release calendar information, description of the data and metadata provided, etc.); and metadata relevant to the exchange of categorization schemes.
  * **SDMX Registry**: Provision is made in the 2.0 standard for standard communication with registry services, to support a data-sharing model of statistical exchange. These services include registration of data and metadata, querying of registered data and metadata, and subscription/notification.
--* **Structural Metadata**: The support for exchange of statistical data and related structural metadata has been expanded. Some support is provided for qualitative data; data cube structures are described; hierarchical code 98 lists are supported; relationships between data structures can be expressed, 99 providing support for extensibility of data structures; and the description of 100 functional dependencies within cubes are supported.
++* **Structural Metadata**: The support for exchange of statistical data and related structural metadata has been expanded. Some support is provided for qualitative data; data cube structures are described; hierarchical code lists are supported; relationships between data structures can be expressed, providing support for extensibility of data structures; and the description of functional dependencies within cubes are supported.
  The major changes from 2.0 to 2.1 can be briefly summarized:
--**Web-Services-Oriented Changes:** Several organizations have been implementing web services applications using SDMX, and these 106 implementations have resulted in several changes to the specifications.
++* **Web-Services-Oriented Changes:** Several organizations have been implementing web services applications using SDMX, and these 106 implementations have resulted in several changes to the specifications. Because the nature of SDMX web services could not be anticipated at the time of the original drafting of the specifications, the web services guidelines have been completely re-developed.
++* **Presentational Changes: **Much work has gone into using various technologies for the visualization of SDMX data and metadata, and some changes have been proposed as a result, to better leverage this graphical visualization. These changes are largely to leverage the Cross-domain Concepts of the Content Oriented Guidelines.
++* **Consistency Issues:** There have been some areas where the draft specifications were inconsistent in minor ways, and these have been addressed.
++* **Clarifications in Documentation:** In some cases it has been identified that the documentation of specific fields within the standard needed clarification and elaboration, and these issues have been addressed.
++* **Optimization for XML Technologies:** Implementation has shown that it is possible to better organize the XML schemas for use within common technology development tools which work with XML. These changes are primarily focused on leveraging the object-oriented features of W3C XML Schema to allow for easier processing of SDMX data and metadata.
++* **Consistency between the SDMX-ML and the SDMX Information Model: **Certain aspects of the XML schemas and UML model have been more closely aligned, to allow for easier comprehension of the SDMX model.
++* **Technical Bugs:** Some minor technical bugs have been identified in the registry interfaces and elsewhere. These bugs have been addressed.
++* **Support for Non-Time-Series Data in the Generic Format: **One area which has been extended is the ability to express non-time-series data as part of the generic data message.
++* **Simplification of the data structure definition - specific message types: **Both time series (version 2.0 Compact) and non-time series data sets (version 2.0 Cross Sectional) use the same underlying structure for a structure-specific formatted message, which is specific to the Data Structure Definition of the data set.
++* **Simplification and better support for the metadata structure: **New use 140 cases have been reported and these are now supported by a re-modelled metadata structure definition.
++* **Support for partial item schemes such as a code list: **The concept of a 143 partial (sub-set) item scheme such as a partial code list for use in exchange scenarios has been introduced**.**
--Because the nature of SDMX web services could not be anticipated at the time of the original drafting of the specifications, the web services guidelines have been completely re-developed.
--
--**Presentational Changes: **Much work has gone into using various technologies for the visualization of SDMX data and metadata, and some changes have been proposed as a result, to better leverage this graphical visualization. These changes are largely to leverage the Cross-domain Concepts of the Content Oriented Guidelines.**&nbsp;**
--
--**Consistency Issues:** There have been some areas where the draft specifications were inconsistent in minor ways, and these have been addressed.
--
--**Clarifications in Documentation:** In some cases it has been identified that the documentation of specific fields within the standard needed clarification and elaboration, and these issues have been addressed.**&nbsp;**
--
--**Optimization for XML Technologies:** Implementation has shown that it is possible to better organize the XML schemas for use within common technology development tools which work with XML. These changes are primarily focused on leveraging the object-oriented features of W3C XML Schema to allow for easier processing of SDMX data and metadata.**&nbsp;**
--
--**Consistency between the SDMX-ML and the SDMX Information Model:**
--
--Certain aspects of the XML schemas and UML model have been more closely aligned, to allow for easier comprehension of the SDMX model.
--
--**Technical Bugs:** Some minor technical bugs have been identified in the registry interfaces and elsewhere. These bugs have been addressed.
--
--**Support for Non-Time-Series Data in the Generic Format: **One area which has been extended is the ability to express non-time-series data as part of the generic data message.**&nbsp;**
--
--**Simplification of the data structure definition - specific message types:**
--
--Both time series (version 2.0 Compact) and non-time series data sets (version 2.0 Cross Sectional) use the same underlying structure for a structure-specific formatted message, which is specific to the Data Structure Definition of the data set.
--
--**Simplification and better support for the metadata structure: **New use 140 cases have been reported and these are now supported by a re-modelled metadata structure definition.
--
--**Support for partial item schemes such as a code list: **The concept of a 143 partial (sub-set) item scheme such as a partial code list for use in exchange scenarios has been introduced**.**
--
--1. (((
  = {{id name="_Toc38910"/}}3. Processes and Business Scope =
--1. (((
  == {{id name="_Toc38911"/}}3.1 Process Patterns ==
--)))
--)))
  SDMX identifies three basic process patterns regarding the exchange of statistical data and metadata. These can be described as follows:
@@ -104,10 +104,7 @@
  It is important to note that SDMX is primarily focused on the //exchange// and //dissemination// of statistical data and metadata. There may also be many uses for the standard model and formats specified here in the context of internal processing of data that are not concerned with the exchange between organizations and users, however. It is felt that a clear, standard formatting of data and metadata for the purposes of exchange and dissemination can also facilitate internal processing by organizations and users, but this is not the focus of the specification.
--1.
--11. (((
  == {{id name="_Toc38912"/}}3.2 SDMX and Process Automation ==
--)))
  Statistical data and metadata exchanges employ many different automated processes, but some are of more general interest than others. There are some common information technologies that are nearly ubiquitous within information systems today. SDMX aims to provide standards that are most useful for these automated processes and technologies.
@@ -120,10 +120,7 @@
  The SDMX standards specified here are designed to support the requirements of all of these automation processes and technologies.
--1.
--11. (((
  == {{id name="_Toc38913"/}}3.3 Statistical Data and Metadata ==
--)))
  To avoid confusion about which "data" and "metadata" are the intended content of the SDMX formats specified here, a statement of scope is offered. Statistical "data" are sets of often numeric observations which typically have time associated with them. They are associated with a set of metadata values, representing specific concepts, which act as identifiers and descriptors of the data. These metadata values and concepts can be understood as the named dimensions of a multi-dimensional co-ordinate system, describing what is often called a "cube" of data.
@@ -143,12 +143,9 @@
  [[image:SDMX_2-1_SECTION_1_Framework_2020-07_b3f80ada.jpg||height="417" width="564"]]
-- **Figure 1: High Level Schematic of Major Artefacts in the SDMX Information Model**
++**Figure 1: High Level Schematic of Major Artefacts in the SDMX Information Model**
--1.
--11. (((
  == {{id name="_Toc38914"/}}3.4 The SDMX View of Statistical Exchange ==
--)))
  Version 1.0 of ISO/TS 17369 SDMX covered statistical data sets and the metadata related to the structure of these data sets. This scope was useful in supporting the different models of statistical exchange (bilateral exchange, gateway exchange, and data-sharing) but was not by itself sufficient to support them completely. Versions 2.0 and 2.1 provide a much more complete view of statistical exchange, so that an open data-sharing model can be fully supported, and other models of exchange can be more completely automated. In order to produce technical standards that will support this increased scope, the SDMX Information Model provides a broader set of formal objects which describe the actors, processes, and resources within statistical exchanges.
@@ -204,10 +204,7 @@
  As with data structures, the generic format for metadata sets provides a known document structure, whilst the structure specific format is derived specifically from a metadata structure definition and can perform a higher degree of schema validation.
--1.
--11. (((
  == {{id name="_Toc38915"/}}3.5 SDMX Registry Services ==
--)))
  In order to provide visibility into the large amount of data and metadata which exists within the SDMX model of statistical exchange, it is felt that an architecture based on a set of registry services is potentially useful. A “registry” – as understood in webservices terminology – is an application which maintains and stores metadata for querying, and which can be used by any other application in the network with sufficient access privileges (though note that the mechanism of access control is outside of the scope of the SDMX standard). It can be understood as the index of a distributed database or metadata repository which is made up of all the data provider’s data sets and reference metadata sets within a statistical community, located across the Internet or similar network.
@@ -222,10 +222,7 @@
  * //**Querying: **//The registry services have interfaces for querying the metadata contained in a registry, so that applications and users can discover the existence of data sets and reference metadata sets, structural metadata, the providers/agencies associated with those objects, and the provider agreements which describe how the data and metadata are made available, and how they are categorized.
  * //**Subscription/Notification:**// It is possible to “subscribe” to specific objects in a registry, so that a notification will be sent to all subscribers whenever the registry objects are updated.
--1.
--11. (((
  == {{id name="_Toc38916"/}}3.6 Web services ==
--)))
  Web services allow computer applications to exchange data directly over the Internet, essentially allowing modular or distributed computing in a more flexible fashion than ever before. In order to allow web services to function, however, many standards are required: for requesting and supplying data; for expressing the enveloping data which is used to package exchanged data; for describing web services to one another, to allow for easy integration into applications that use other web services as data resources.
@@ -238,9 +238,7 @@
  A normative list of common error codes: When web services are used, it is necessary to have error codes which can help to explain the situation when problems are encountered. Prior to version 2.1 of the SDMX standard, there was no set of agreed error codes for use with SDMX web services. Version 2.1 of the SDMX standard fills that gap.
--1. (((
  = {{id name="_Toc38917"/}}4 The SDMX Information Model =
--)))
  SDMX provides a way of modelling statistical data, and defines the set of metadata constructs used for this purpose. Because SDMX specifies formats in two syntaxes for expressing data and structural metadata, the model is used as a mechanism for guaranteeing that transformation between the different formats are lossless. All of the formats are syntax-bound expressions of the common information model. SDMX version 1.0 has based itself on GESMES/TS as an input to the model and formats, both to build on the proven success of this model for time series data exchange, and to ensure backward compatibility with existing GESMES/TS-based systems. Version 2.0/2.1 expands upon the version 1.0 basis to provide a more comprehensive model.
@@ -256,9 +256,7 @@
  The SDMX Information Model is presented using UML, and is also described in prose. While the information model is not normative, it is a valuable tool for understanding and using the normative format specifications.
--1. (((
  = {{id name="_Toc38918"/}}5 SDMX-EDI =
--)))
  The SDMX-EDI format is drawn from the GESMES/TS version 3.0 implementation guide, as published as a standard of the SDMX initiative.
@@ -270,17 +270,12 @@
  EDIFACT syntax used for SDMX-EDI, and those found in the XML syntax of SDMXML. Since both syntactic implementations reflect the same logical constructs, SDMXEDI data and structural metadata messages can be transformed into corresponding SDMX-ML formats, and vice-versa. Thus, these standards provide for interoperability between the UN/EDIFACT-based and XML-based systems processing and exchanging statistical data and metadata.
--1. (((
  = {{id name="_Toc38919"/}}6 SDMX-ML =
--)))
  While the SDMX-EDI format is primarily designed to support batch exchange, SDMXML supports a wider range of requirements. XML formats are used for many different types of automated processing, and thus must support more varied processing scenarios. That is why there are several types of messages available as SDMX-ML formats. Each is suited to support a specific set of processing requirements.
 . //Structure Definition~:// All SDMX-ML message types share a common XML expression of the metadata needed to understand and process a data set or metadata set, and additional metadata about category schemes and organisations is included. Also, the structural aspects of data and metadata provision – dataflows and metadataflows – are described using this format.
--1. //Generic Data~:// All statistical data expressible in SDMX-ML can be marked up according to this data format, in agreement with the contents of a Structure Definition message. It is designed for any scenario where applications receiving the data need to process it according to a single format. Such applications may need independent access to the data set's structure before they process it. Data marked up in this format are not particularly compact, but they make easily available all aspects of the data set. This format does
--
--not provide strict validation between the data set and its structural definition using a generic XML parser. It supports the transmission of partial data sets (incremental updates) as well as whole data sets. It supports both the timeseries and the cross-sectional use cases.
--
++1. //Generic Data~:// All statistical data expressible in SDMX-ML can be marked up according to this data format, in agreement with the contents of a Structure Definition message. It is designed for any scenario where applications receiving the data need to process it according to a single format. Such applications may need independent access to the data set's structure before they process it. Data marked up in this format are not particularly compact, but they make easily available all aspects of the data set. This format does not provide strict validation between the data set and its structural definition using a generic XML parser. It supports the transmission of partial data sets (incremental updates) as well as whole data sets. It supports both the timeseries and the cross-sectional use cases.
 . //Structure-specific Data~:// This format is specific to the Data Structure Definition of the data set (in other terms, it is DSD-specific) and is created by following mappings between the metadata constructs defined in the Structure Definition message and the technical specification of the format. It supports the exchange of large data sets in XML format (typically the size of the data set is 50% of the same data expressed as Generic Data), provides strict validation of conformance with the DSD using a generic XML parser, and supports the transmission of partial data sets (incremental updates) as well as whole data sets. The Structure-specific Data format specified in SDMX 2.1 supports both the time-series and the cross-sectional use cases which were covered by two distinct formats in SDMX 2.0. Many XML tools and technologies have expectations about the functions performed by an XML schema, one of which is a very direct relationship between the XML constructs described in the XML schema and the tagged data in the XML instance. Strong data typing is also considered normal, supporting full validation of the tagged data. These message types are designed to support validation and other expected XML schema functions.
 . //Generic Metadata~:// All reference metadata expressible in SDMX-ML format can be marked up according to this schema. It performs only a minimum of validation, and is somewhat verbose, but it does support the creation of generic software tools and services for processing reference metadata.
 . //Structure-specific Metadata~:// For each metadata structure definition, an XML schema specific to that structure can be created, to perform validation on sets of reported metadata. This structure is less verbose than the Generic Metadata format, and, because the XML mark-up relates directly to the reported concepts, it is appropriate for applications that are designed to process a specific type of metadata report. It is analogous to the Structurespecific Data format for data in its approach to the use of XML.
@@ -289,61 +289,42 @@
  Because all of the SDMX-ML formats are implementations of the same information model, and all the data and metadata messages are derivable from the Structure message which describes a data set or metadata set, it is possible to have standard mappings between each of the similar formats. These mappings can be implemented in generic transformation tools, useful to all SDMX-ML users, and not specific to a particular data set’s key family or metadata set’s structure definition (even though some of the formats they deal with may be). Part of the SDMX-ML package is the set of mappings between the structure-specific data and metadata formats and the Structure Definition format from which all are derivable.
--1. (((
  = {{id name="_Toc38920"/}}7 Conformance =
--)))
  This section will contain a normative statement of what applications must do to be considered conformant with the SDMX version 2.1 specifications. This will address both the application functionality that must be supported, and the contents of an Implementer’s Conformance Statement regarding SDMX conformance.
--1. (((
  = {{id name="_Toc38921"/}}8 Dependencies on SDMX content-oriented guidelines =
--)))
  The technical standards proposed here are designed so that they can be used in conjunction with other SDMX guidelines which are more closely tied to the content and semantics of statistical data exchange. The SDMX Information Model works equally well with any statistical concept, but to encourage interoperability, it is also necessary to standardize and harmonize the use of specific concepts and terminology. To achieve this goal, SDMX creates and maintains guidelines for crossdomain concepts, terminology, and structural definitions. There are three major parts to this effort.
--1.
--11. (((
  == {{id name="_Toc38922"/}}8.1 Cross-Domain Concepts ==
--)))
  The SDMX Cross-Domain Concepts is a content guideline concerning concepts which are used across statistical domains. This list is expected to grow and to be subject to revision as SDMX is used in a growing number of domains. The use of the SDMX Cross-Domain Concepts, where appropriate, provides a framework to further promote interoperability among organisations using the technical standards presented here. The harmonization of statistical concepts includes not only the definitions of the concepts, and their names, but also, where appropriate, their representation with standard code lists, and the role they play within data structure definitions and metadata structure definitions.
  The intent of this guideline is two-fold: to provide a core set of concepts which can be used to structure statistical data and metadata, to promote interoperability between systems (“structural metadata”, as described above); and to promote the exchange of metadata more widely, with a set of harmonized concept names and definitions for other types of metadata (“reference metadata”, as defined above.)
--1.
--11. (((
  == {{id name="_Toc38923"/}}8.2 Metadata Common Vocabulary ==
--)))
  The Metadata Common Vocabulary is an SDMX guideline which provides definition of terms to be used for the comparison and mapping of terminology found in data structure definitions and in other aspects of statistical metadata management. Essentially, it provides ISO-compliant definitions for a wide range of statistical terms, which may be used directly, or against which other terminology systems may be mapped. This set of terms is inclusive of the terminology used within the SDMX Technical Standards.
  The MCV provides definitions for terms on which the SDMX Cross-Domain Metadata Concepts work is built.
--1.
--11. (((
  == {{id name="_Toc38924"/}}8.3 Statistical Subject-Matter Domains ==
--)))
  The Statistical Subject-Matter Domains is a listing of the breadth of statistical information for the purposes of organizing widespread statistical exchange and categorization. It acts as a standard scheme against which the categorization schemes of various counterparties can be mapped, to facilitate interoperable data and metadata exchange. It serves another useful purpose, however, which is to allow an organization of corresponding “domain groups”, each of which could define standard data structure definitions, concepts, etc. within their domains. Such groups already exist within the international community. SDMX would use the Statistical Subject-Matter Domains list to facilitate the efforts of these groups to develop the kinds of content standards which could support the interoperation of SDMXconformant technical systems within and across statistical domains. The organisation of the content of such schemes is supported in SDMX as a Category Scheme.
  SDMX Statistical Subject-Matter Domains will be listed and maintained by the SDMX Initiative and will be subject to adjustment.
--1. (((
  = {{id name="_Toc38925"/}}9 Looking Forward =
--)))
  The SDMX initiative sees this set of data and metadata formats and registry services interfaces standards as useful in creating more efficient and open systems for statistical exchange. It is anticipated that SDMX will refine these standards further as they are implemented, so as to build on the interoperability enabled by having a set of standard formats and exchanges based on a common information model.
  The review process for version 2.0 and 2.1 has suggested that future work should take advantage of a wider participation of the SDMX user community (statistical offices, central banks and other national and international organisations dealing with statistics) in further enhancing the Technical Standards and improving its use.
--1. (((
  = {{id name="_Toc38926"/}}10 Validation and Transformation Language =
--)))
--For many years the SDMX initiative has been fostering and supporting the development of a standard calculation language, called Validation and Transformation Language (VTL). A blueprint for defining calculations was already described in the original SDMX 2.1 specifications (package 13 of the Information
++For many years the SDMX initiative has been fostering and supporting the development of a standard calculation language, called Validation and Transformation Language (VTL). A blueprint for defining calculations was already described in the original SDMX 2.1 specifications (package 13 of the Information Model - “Transformations and Expressions”). It was just a basic framework that required further developments to became operational in order to achieve a calculation language able to manipulate SDMX artefacts.
--Model - “Transformations and Expressions”). It was just a basic framework that required further developments to became operational in order to achieve a calculation language able to manipulate SDMX artefacts.
--
  These developments started in late 2012 and were put in charge of the Validation and Transformation Language Task Force (VTL TF), which included members of the SDMX Technical Working Group (TWG) and Statistical Working Group (SWG), besides experts coming from the DDI and GSIM communities. The intent was to define a stardard language to be implemented in SDMX and applicable also to GSIM and DDI. This brought to the publication of the VTL 1.0 in 2015. Then new requirements came from a number of proofs of concepts and tests of VTL 1.0 made by several organisations and triggered a large improvement of the language. A new provisional version, the VTL 1.1, was released in public consultation in 2017. The high number of comments received triggered another phase of intensive work, with the main goal of achieving a more robust and forward compatible version. Finally, the VTL 2.0 was published between April and July 2018 (see the SDMX website).
  The implementation in the SDMX standards of the VTL 2.0 started in late 2018. It allows to write VTL 2.0 programs for validating and transforming SDMX data, to store these programs in a SDMX metadata registry and to exchange them through SDMX messages, also together the definition of the data structures of the involved data.
@@ -352,10 +352,8 @@
  The new SDMX 2.1 parts relevant to VTL are in Section 2 (Information Model), Section 3A (SDMX-ML: XML formats), Section 3B (SDMX-ML: XML Schema, Samples, WADL and WSDL), Section 5 (Registry Specifications), Section 6 (Technical Notes) and in the REST specifications of the SDMX web services. On the contrary, the VTL is not supported in the UN/EDIFACT SDMX formats (Section 4) and in the SDMX SOAP web service interface.
--As for the Section 2 (Information Model), the change is relevant to the package 13
++As for the Section 2 (Information Model), the change is relevant to the package 13 “Transformations and Expressions”, which previously contained only a blueprint for future elaboration and was not operational. This package is renamed to “Validation and Transformation Language” and is completely reformulated by introducing the actual object classes needed to define and manage VTL 2.0 programs. The other parts of the IM are not impacted.
--“Transformations and Expressions”, which previously contained only a blueprint for future elaboration and was not operational. This package is renamed to “Validation and Transformation Language” and is completely reformulated by introducing the actual object classes needed to define and manage VTL 2.0 programs. The other parts of the IM are not impacted.
--
  In the Section 3A and 3B, new schemas, samples and documentation aimed at exchanging VTL programs through SDMX structure messages have been introduced. Other parts are not impacted.
  In the section 5 (Registry Specifications), the VTL artefacts have been added. The other artefacts are not impacted.
@@ -364,4 +364,6 @@
  Finally, new REST interfaces for VTL have been added. These are not maintained any more in the section 7; the link to these specifications can be found on the SDMX website.
--[[1>>path:#sdfootnote1anc||name="sdfootnote1sym"]] SOAP and REST specifications are not maintained any more in this section, see the SDMX website.
++----
++
++{{putFootnotes/}}

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