Changes for page 4 General Notes for Implementers

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	1	+Methodology.SDMX 3\.0 Standards\. Technical notes.WebHome

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  === {{id name="_Toc291517"/}}4.2.11 Notes on Formats ===
--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.
++There is no ambiguity in these formats so that for any given value of time, the [[category>>doc:xwiki:Glossary.Category.WebHome]] of the period (and thus the intended [[time period>>doc:xwiki:Glossary.Time period.WebHome]] 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.
  === {{id name="_Toc291518"/}}4.2.12 Effect on Time Ranges ===
--All SDMX-ML data messages are capable of functioning in a manner similar to SDMXEDI 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.
++All [[SDMX-ML>>doc:xwiki:Glossary.SDMX-ML.WebHome]] data messages are capable of functioning in a manner similar to SDMXEDI if the [[Dimension>>doc:xwiki:Glossary.Dimension.WebHome]] at the observation (% style="color:#2ecc71" %)level(%%) is time: the [[time period>>doc:xwiki:Glossary.Time period.WebHome]] 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.
  === 4.2.13 Time in Query Messages ===
--When querying for time values, the value of a time parameter can be provided as any of the Observational Time Period formats and must be paired with an operator. This section will detail how systems processing query messages should interpret these parameters.
++When querying for time values, the value of a time parameter can be provided as any of the Observational [[Time Period>>doc:xwiki:Glossary.Time period.WebHome]] formats and must be paired with an operator. This section will detail how systems processing query messages should interpret these parameters.
--Fundamental to processing a time value parameter in a query message is understanding that all time periods should be handled as a distinct range of time. Since the time parameter in the query is paired with an operator, this also effectively represents a distinct range of time. Therefore, a system processing the query must simply match the data where the time period for requested parameter is encompassed by the time period resulting from value of the query parameter. The following table details how the operators should be interpreted for any time period provided as a parameter.
++Fundamental to processing a time value parameter in a query message is understanding that all [[time periods>>doc:xwiki:Glossary.Time period.WebHome]] should be handled as a distinct range of time. Since the time parameter in the query is paired with an operator, this also effectively represents a distinct range of time. Therefore, a system processing the query must simply match the data where the [[time period>>doc:xwiki:Glossary.Time period.WebHome]] for requested parameter is encompassed by the [[time period>>doc:xwiki:Glossary.Time period.WebHome]] resulting from value of the query parameter. The following table details how the operators should be interpreted for any [[time period>>doc:xwiki:Glossary.Time period.WebHome]] provided as a parameter.
  (% style="width:1020.29px" %)
  |(% style="width:236px" %)**Operator**|(% style="width:781px" %)**Rule**
@@ -434,7 +434,7 @@
  |(% style="width:236px" %)Less Than or Equal To|(% style="width:781px" %)Any data on or before the last moment of the period
  |(% style="width:236px" %)Equal To|(% style="width:781px" %)Any data which falls on or after the first moment of the period and before or on the last moment of the period
--Reporting Time Periods as query parameters are handled like this: any data within the bounds of the reporting period for the year is matched, regardless of the actual start day of the reporting year. In addition, data reported against a normal calendar period is matched if it falls within the bounds of the time parameter based on a reporting year start day of January 1. When determining whether another reporting period falls within the bounds of a report period query parameter, one will have to take into account the actual time period to compare weeks and days to higher order report periods. This will be demonstrated in the examples to follow.
++Reporting [[Time Periods>>doc:xwiki:Glossary.Time period.WebHome]] as query parameters are handled like this: any data within the bounds of the reporting period for the year is matched, regardless of the actual start day of the reporting year. In addition, data reported against a normal calendar period is matched if it falls within the bounds of the time parameter based on a reporting year start day of January 1. When determining whether another reporting period falls within the bounds of a report period query parameter, one will have to take into account the actual [[time period>>doc:xwiki:Glossary.Time period.WebHome]] to compare weeks and days to higher order report periods. This will be demonstrated in the examples to follow.
  **Examples:**
@@ -448,12 +448,12 @@
  * 2011-01-01 or later
  * 2011-01-01/P[Any Duration] or any later start date
  * 2011-[Any reporting period] (any reporting year start day)
--* 2010-S2 (reporting year start day ~-~-07-01 or later)
--* 2010-T3 (reporting year start day ~-~-07-01 or later)
--* 2010-Q3 or later (reporting year start day ~-~-07-01 or later)
--* 2010-M07 or later (reporting year start day ~-~-07-01 or later)
--* 2010-W28 or later (reporting year start day ~-~-07-01 or later)
--* 2010-D185 or later (reporting year start day ~-~-07-01 or later)
++* 2010-S2 (reporting year start day 07-01 or later)
++* 2010-T3 (reporting year start day 07-01 or later)
++* 2010-Q3 or later (reporting year start day 07-01 or later)
++* 2010-M07 or later (reporting year start day 07-01 or later)
++* 2010-W28 or later (reporting year start day 07-01 or later)
++* 2010-D185 or later (reporting year start day 07-01 or later)
  **Reporting Period**
  Query Parameter: Greater than or equal to 2010-Q3
@@ -469,91 +469,91 @@
  * 2010-T3 (any reporting year start day)
  * 2010-Q3 or later (any reporting year start day)
  * 2010-M07 or later (any reporting year start day)
--* 2010-W27 or later (reporting year start day ~-~-01-01)^^5^^ • 2010-D182 or later (reporting year start day ~-~-01-01)
--* 2010-W28 or later (reporting year start day ~-~-07-01)^^6^^
--* 2010-D185 or later (reporting year start day ~-~-07-01)
++* 2010-W27 or later (reporting year start day 01-01)^^5^^ • 2010-D182 or later (reporting year start day 01-01)
++* 2010-W28 or later (reporting year start day 07-01)^^6^^
++* 2010-D185 or later (reporting year start day 07-01)
  == 4.3 Versioning ==
--Versioning operates at the level of versionable and maintainable objects in the SDMX information model. Within the SDMX Structure and MetadataSet messages, there is a well-defined pattern for artefact versioning and referencing. The artefact identifiers are qualified by their version numbers – that is, an object with an Agency of "A", and ID of "X" and a version of "1.0.0" is a different object than one with an Agency of "A", an ID of "X", and a version of "1.1.0".
++Versioning operates at the (% style="color:#2ecc71" %)level(%%) of versionable and maintainable objects in the [[SDMX information model>>doc:xwiki:Glossary.SDMX Information Model.WebHome]]. Within the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] Structure and MetadataSet messages, there is a well-defined pattern for [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] versioning and referencing. The [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] identifiers are qualified by their (% style="color:#2ecc71" %)version(%%) numbers – that is, an object with an Agency of "A", and ID of "X" and a (% style="color:#2ecc71" %)version(%%) of "1.0.0" is a different object than one with an Agency of "A", an ID of "X", and a (% style="color:#2ecc71" %)version(%%) of "1.1.0".
--As of SDMX 3.0, the versioning rules are extended to allow for truly versioned artefacts through the implementation of the rules of the well-known practice called "Semantic Versioning" ([[__http:~~/~~/semver.org__>>https://http:semver.org]]), in addition to the legacy non-restrictive versioning scheme. In addition, the "isFinal" property is removed from //MaintainableArtefact//. According to the legacy versioning, any artefact defined without a version is equivalent to following the legacy versioning, thus having version ‘1.0’.
++As of [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] 3.0, the versioning rules are extended to allow for truly versioned [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] through the implementation of the rules of the well-known practice called "Semantic Versioning" ([[__http:~~/~~/semver.org__>>https://http:semver.org]]), in addition to the legacy non-restrictive versioning scheme. In addition, the "isFinal" property is removed from //MaintainableArtefact//. According to the legacy versioning, any [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] defined without a (% style="color:#2ecc71" %)version(%%) is equivalent to following the legacy versioning, thus having (% style="color:#2ecc71" %)version(%%) ‘1.0’.
  === 4.3.1 Non-versioned artefacts ===
--Indeed, some use cases do not need or are incompatible with versioning for some or all their structural artefacts, such as the Agency, Data Providers, Metadata Providers and Data Consumer Schemes. These artefacts follow the legacy versioning, with a fixed version set to ‘1.0’.
++Indeed, some use cases do not need or are incompatible with versioning for some or all their structural [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]], such as the Agency, [[Data Providers>>doc:xwiki:Glossary.Data provider.WebHome]], Metadata Providers and [[Data Consumer Schemes>>doc:xwiki:Glossary.Data consumer scheme.WebHome]]. These [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] follow the legacy versioning, with a fixed (% style="color:#2ecc71" %)version(%%) set to ‘1.0’.
--Many existing organisation’s data management systems work with version-less structures and apply ad-hoc structural metadata governance processes. The new nonversioned artefacts will allow supporting those numerous situations, where organisations do not manage version numbers.
++Many existing organisation’s data management systems work with (% style="color:#2ecc71" %)version(%%)-less structures and apply ad-hoc [[structural metadata>>doc:xwiki:Glossary.Structural metadata.WebHome]] governance processes. The new nonversioned [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] will allow supporting those numerous situations, where organisations do not manage (% style="color:#2ecc71" %)version(%%) numbers.
--2010-Q3 (with a reporting year start day of ~-~-01-01) starts on 2010-07-01. This is day 4 of week 26, therefore the first week matched is week 27.
++2010-Q3 (with a reporting year start day of 01-01) starts on 2010-07-01. This is day 4 of week 26, therefore the first week matched is week 27.
--2010-Q3 (with a reporting year start day of ~-~-07-01) starts on 2011-01-01. This is day 6 of week 27, therefore the first week matched is week 28.
++2010-Q3 (with a reporting year start day of 07-01) starts on 2011-01-01. This is day 6 of week 27, therefore the first week matched is week 28.
  === 4.3.2 Semantically versioned artefacts ===
--Since the purpose of SDMX versioning is to allow communicating the structural artefact changes to data exchange partners and connected systems, SDMX 3.0 offers Semantic Versioning (aka SemVer) with a clear and unambiguous syntax to all semantically versioned SDMX 3.0 structural artefacts. Semantic versioning will thus better respond to situations where the SDMX standard itself is the only structural contract between data providers and data consumers and where changes in structures can only be communicated through the version number increases.
++Since the purpose of [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] versioning is to allow communicating the structural [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] changes to data exchange partners and connected systems, [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] 3.0 offers Semantic Versioning (aka SemVer) with a clear and unambiguous syntax to all semantically versioned [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] 3.0 structural [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]]. Semantic versioning will thus better respond to situations where the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] standard itself is the only structural contract between [[data providers>>doc:xwiki:Glossary.Data provider.WebHome]] and [[data consumers>>doc:xwiki:Glossary.Data consumer.WebHome]] and where changes in structures can only be communicated through the (% style="color:#2ecc71" %)version(%%) number increases.
--The semantic version number consists of four parts: MAJOR, MINOR, PATCH and EXTENSION, the first three parts being separated by a dot (.), the last two parts being separated by a hyphen (-): MAJOR.MINOR.PATCH-EXTENSION. All versions are ordered.
++The semantic (% style="color:#2ecc71" %)version(%%) number consists of four parts: MAJOR, MINOR, PATCH and EXTENSION, the first three parts being separated by a dot (.), the last two parts being separated by a hyphen : MAJOR.MINOR.PATCH-EXTENSION. All (% style="color:#2ecc71" %)versions(%%) are ordered.
  The detailed rules for semantic versioning are listed in chapter 14 in the annex for “Semantic Versioning”. In short, they define:
--Given a version number MAJOR.MINOR.PATCH (without EXTENSION), when making changes to that semantically versioned SDMX artefact, then one must increment the:
++Given a (% style="color:#2ecc71" %)version(%%) number MAJOR.MINOR.PATCH (without EXTENSION), when making changes to that semantically versioned [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]], then one must increment the:
--1. MAJOR version when backwards incompatible artefact changes are made,
--1. MINOR version when artefact elements are added in a backwards compatible manner, or
--1. PATCH version when backwards compatible artefact property changes are made.
++1. MAJOR (% style="color:#2ecc71" %)version(%%) when backwards incompatible [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] changes are made,
++1. MINOR (% style="color:#2ecc71" %)version(%%) when [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] elements are added in a backwards compatible manner, or
++1. PATCH (% style="color:#2ecc71" %)version(%%) when backwards compatible [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] property changes are made.
--When incrementing a version part, the right-hand side parts are 0-ed (reset to ‘0’).
++When incrementing a (% style="color:#2ecc71" %)version(%%) part, the right-hand side parts are 0-ed (reset to ‘0’).
  Extensions can be added, changed or dropped.
--iven an extended version number MAJOR.MINOR.PATCH-EXTENSION, when making changes to that versioned artefact, then one is not required to increment the version if those changes are within the allowed scope of the version increment from the previous version (if that existed); otherwise, the above version increment rules apply. EXTENSIONs can be used e.g., for drafting or a pre-release.
++iven an extended (% style="color:#2ecc71" %)version(%%) number MAJOR.MINOR.PATCH-EXTENSION, when making changes to that versioned [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]], then one is not required to increment the (% style="color:#2ecc71" %)version(%%) if those changes are within the allowed scope of the (% style="color:#2ecc71" %)version(%%) increment from the previous (% style="color:#2ecc71" %)version(%%) (if that existed); otherwise, the above (% style="color:#2ecc71" %)version(%%) increment rules apply. EXTENSIONs can be used e.g., for drafting or a pre-release.
--Semantically versioned SDMX artefacts will thus be safe to use. Specific version patterns allow them to become either immutable, i.e., the maintainer commits to never change their content, or changeable only within a well-defined scope. If any further change is required, a new version must be created first. Furthermore, the impact of the further change is communicated using a clear version increment. The built-in version extension facility allows for eased drafting of new SDMX artefact versions.
++Semantically versioned [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] will thus be safe to use. Specific (% style="color:#2ecc71" %)version(%%) patterns allow them to become either immutable, i.e., the maintainer commits to never change their content, or changeable only within a well-defined scope. If any further change is required, a new (% style="color:#2ecc71" %)version(%%) must be created first. Furthermore, the impact of the further change is communicated using a clear (% style="color:#2ecc71" %)version(%%) increment. The built-in (% style="color:#2ecc71" %)version(%%) extension facility allows for eased drafting of new [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] (% style="color:#2ecc71" %)versions(%%).
--The production versions of identifiable artefacts are assumed stable, i.e., they do not have an EXTENSION. This is because once in production, an artefact cannot change in any way, or it must change the version. For cases where an artefact is not static, like during the drafting, the version must indicate this by including an EXTENSION. Draft artefacts should not be used outside of a specific system designed to accommodate them. For most purposes, all artefacts should become stable before being used in production.
++The production (% style="color:#2ecc71" %)versions(%%) of [[identifiable artefacts>>doc:xwiki:Glossary.Identifiable artefact.WebHome]] are assumed stable, i.e., they do not have an EXTENSION. This is because once in production, an [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] cannot change in any way, or it must change the (% style="color:#2ecc71" %)version(%%). For cases where an [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] is not static, like during the drafting, the (% style="color:#2ecc71" %)version(%%) must indicate this by including an EXTENSION. Draft [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] should not be used outside of a specific system designed to accommodate them. For most purposes, all [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] should become stable before being used in production.
  === 4.3.3 Legacy-versioned artefacts ===
--Organisations wishing to keep a maximum of backwards compatibility with existing implementations can continue using the previous 2-digit convention for version numbers (MAJOR.MINOR) as in the past, such as '2.3', but without the ‘isFinal’ property. The new SDMX 3.0 standard does not add any strict rules or guarantees about changes in those artefacts, since the legacy versioning rules were rather loose and non-binding, including the meaning of the ‘isFinal’ property, and their implementations were varying.
++Organisations wishing to keep a maximum of backwards compatibility with existing implementations can continue using the previous 2-digit convention for (% style="color:#2ecc71" %)version(%%) numbers (MAJOR.MINOR) as in the past, such as '2.3', but without the ‘isFinal’ property. The new [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] 3.0 standard does not add any strict rules or guarantees about changes in those [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]], since the legacy versioning rules were rather loose and non-binding, including the meaning of the ‘isFinal’ property, and their implementations were varying.
--In order to make artefacts immutable or changes truly predictable, a move to the new semantic versioning syntax is required.
++In order to make [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] immutable or changes truly predictable, a move to the new semantic versioning syntax is required.
  === 4.3.4 Dependency management and references ===
--New flexible dependency specifications with wildcarding allow for easier data model maintenance and enhancements for semantically versioned SDMX artefacts. This allows implementing a smart referencing mechanism, whereby an artefact may reference:
++New flexible dependency specifications with wildcarding allow for easier data model maintenance and enhancements for semantically versioned [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]]. This allows implementing a smart referencing mechanism, whereby an [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] may reference:
--* a fixed version of another artefact
--* the **latest available** version of another artefact
--* the **latest backward compatible** version of another artefact, or the **latest backward and forward** **compatible** version of another artefact.
++* a fixed (% style="color:#2ecc71" %)version(%%) of another [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]]
++* the **latest available** (% style="color:#2ecc71" %)version(%%) of another [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]]
++* the **latest backward compatible** (% style="color:#2ecc71" %)version(%%) of another [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]], or the **latest backward and forward** **compatible** (% style="color:#2ecc71" %)version(%%) of another [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]].
--References not representing a strict artefact dependency, such as the target artefacts defined in a MetadataProvisionAgreement allow for linking to **all currently available** versions of another artefact. Another illustrative case for such loose referencing is that of Constraints and flows. A Constraint may reference many Dataflows or Metadataflows, the addition of more references to flow objects does not version the Constraint. This is because the Constraints are not properties of the flows – they merely make references to them.
++References not representing a strict [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] dependency, such as the target [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] defined in a MetadataProvisionAgreement allow for linking to **all currently available** (% style="color:#2ecc71" %)versions(%%) of another [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]]. Another illustrative case for such loose referencing is that of (% style="color:#2ecc71" %)Constraints(%%) and flows. A (% style="color:#2ecc71" %)Constraint(%%) may reference many [[Dataflows>>doc:xwiki:Glossary.Dataflow.WebHome]] or [[Metadataflows>>doc:xwiki:Glossary.Metadataflow.WebHome]], the addition of more references to flow objects does not (% style="color:#2ecc71" %)version(%%) the (% style="color:#2ecc71" %)Constraint(%%). This is because the (% style="color:#2ecc71" %)Constraints(%%) are not properties of the flows – they merely make references to them.
--Semantically versioned artefacts must only reference other semantically versioned artefacts, which may include extended versions. Non-versioned and legacy-versioned artefacts can reference any other non-versioned or versioned (whether semantic or legacy) artefacts. The scope of wildcards in references adapts correspondingly.
++Semantically versioned [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] must only reference other semantically versioned [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]], which may include extended (% style="color:#2ecc71" %)versions(%%). Non-versioned and legacy-versioned [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]] can reference any other non-versioned or versioned (whether semantic or legacy) [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]]. The scope of wildcards in references adapts correspondingly.
--The mechanism named "early binding" refers to a dependency on a stable versioned artefact – everything with a stable versioned identity is a known quantity and will not change. The "late binding" mechanism is based on a wildcarded reference, and it resolves that reference and determines the currently related artefact at runtime.
++The mechanism named "early binding" refers to a dependency on a stable versioned [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] – everything with a stable versioned identity is a known quantity and will not change. The "late binding" mechanism is based on a wildcarded reference, and it resolves that reference and determines the currently related [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] at runtime.
--One area which is much impacted by this versioning scheme is the ability to reference external objects. With the many dependencies within the various structural objects in SDMX, it is useful to have a scheme for external referencing. This is done at the level of maintainable objects (DSDs, Codelists, Concept Schemes, etc.) In an SDMX Structure Message, whenever an "isExternalReference" attribute is set to true, then the application must resolve the address provided in the associated "uri" attribute and use the SDMX Structure Message stored at that location for the full definition of the object in question. Alternately, if a registry "urn" attribute has been provided, the registry can be used to supply the full details of the object.
++One area which is much impacted by this versioning scheme is the ability to reference external objects. With the many dependencies within the various structural objects in [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]], it is useful to have a scheme for external referencing. This is done at the (% style="color:#2ecc71" %)level(%%) of maintainable objects (DSDs, Codelists, [[Concept Schemes>>doc:xwiki:Glossary.Concept scheme.WebHome]], etc.) In an [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] Structure Message, whenever an [[isExternalReference>>doc:xwiki:Glossary.isExternalReference.WebHome]] [[attribute>>doc:xwiki:Glossary.Attribute.WebHome]] is set to true, then the application must resolve the address provided in the associated "uri" [[attribute>>doc:xwiki:Glossary.Attribute.WebHome]] and use the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] Structure Message stored at that location for the full definition of the object in question. Alternately, if a registry "urn" [[attribute>>doc:xwiki:Glossary.Attribute.WebHome]] has been provided, the registry can be used to supply the full details of the object.
  The detailed rules for dependency management and references are listed in chapter 14 in the annex for “Semantic Versioning”.
--In order to allow resolving the described new forms of dependencies, the SDMX 3.0 Rest API supports retrievals legacy-versioned, wildcarded and extended artefact versions:
++In order to allow resolving the described new forms of dependencies, the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] 3.0 Rest API supports retrievals legacy-versioned, wildcarded and extended [[artefact>>doc:xwiki:Glossary.Artefact.WebHome]] (% style="color:#2ecc71" %)versions(%%):
--* Artefact queries for a **specific** version (X.Y, X.Y.Z or X.Y.Z-EXT).
--* Artefact queries for **latest available** semantic versions within the wildcard scope (X+.Y.Z, X.Y+.Z or X.Y.Z+).
--* Queries for **non-versioned** artefacts.
--* Artefact queries for **all available** semantic versions within the wildcard scope (*, X.* or X.Y.*), where only the first form is required for resolving wildcarded loose references.
++* [[Artefact>>doc:xwiki:Glossary.Artefact.WebHome]] queries for a **specific** (% style="color:#2ecc71" %)version(%%) (X.Y, X.Y.Z or X.Y.Z-EXT).
++* [[Artefact>>doc:xwiki:Glossary.Artefact.WebHome]] queries for **latest available** semantic (% style="color:#2ecc71" %)versions(%%) within the wildcard scope (X+.Y.Z, X.Y+.Z or X.Y.Z+).
++* Queries for **non-versioned** [[artefacts>>doc:xwiki:Glossary.Artefact.WebHome]].
++* [[Artefact>>doc:xwiki:Glossary.Artefact.WebHome]] queries for **all available** semantic (% style="color:#2ecc71" %)versions(%%) within the wildcard scope (*, X.* or X.Y.*), where only the first form is required for resolving wildcarded loose references.
--The combination of wildcarded queries with a specific version extension is not permitted.
++The combination of wildcarded queries with a specific (% style="color:#2ecc71" %)version(%%) extension is not permitted.
--Full details can be found in the SDMX RESTful web services specification.
++Full details can be found in the [[SDMX>>doc:xwiki:Glossary.Statistical data and metadata exchange.WebHome]] RESTful web services specification.
  == 4.4 Structural Metadata Querying Best Practices ==
--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.
++When querying for [[structural metadata>>doc:xwiki:Glossary.Structural metadata.WebHome]], 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.
--Any structural metadata object which contains a reference to an object can be queried based on that reference. For example, a categorisation references both a category and the object is it categorising. As this is the case, one can query for categorisations which categorise a particular object or which categorise against a particular category or category scheme. This mechanism should be used when the referenced object is known.
++Any [[structural metadata>>doc:xwiki:Glossary.Structural metadata.WebHome]] object which contains a reference to an object can be queried based on that reference. For example, a categorisation references both a [[category>>doc:xwiki:Glossary.Category.WebHome]] and the object is it categorising. As this is the case, one can query for categorisations which categorise a particular object or which categorise against a particular [[category>>doc:xwiki:Glossary.Category.WebHome]] or [[category scheme>>doc:xwiki:Glossary.Category scheme.WebHome]]. This mechanism should be used when the referenced object is known.
--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.
++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>>doc:xwiki:Glossary.Category scheme.WebHome]] and the related categorisations for a given [[maintenance agency>>doc:xwiki:Glossary.Maintenance agency.WebHome]]. In this case, one could query for the [[category scheme>>doc:xwiki:Glossary.Category scheme.WebHome]] by the [[maintenance agency>>doc:xwiki:Glossary.Maintenance agency.WebHome]] and specify that parent and sibling references should be resolved. This would result in the categorisations which reference the [[categories>>doc:xwiki:Glossary.Category.WebHome]] in the matched schemes to be returned, as well as the object which they categorise.
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