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Linking mechanism

Object optional. A link to an external resource.

  • href - String optional only if urn is present. Absolute or relative URL of the external resource.
  • rel - String. Relationship of the object to the external resource. See semantics below.
  • urn - String optional only if href is present. The urn holds a valid SDMX Registry URN (see SDMX Registry Specification for details).
  • uri - String optional. The uri attribute holds a URI that contains a link to additional information about the resource, such as a web page. This uri is not an SDMX resource.
  • title - String optional. A human-readable (best-language-match) description of the target link.
  • titles - Object optional. A list of human-readable localised descriptions (see names) of the target link.
  • type - String optional. A hint about the type of representation returned by the link.
  • hreflang - String optional. The natural language of the external link, the same as used in the HTTP Accept-Language request header.

See the section on localised text elements on how the message deals with languages.

Example 
{
  "href": "https://registry.sdmx.org/ws/rest/datastructure/ECB/ECB_EXR1",
  "rel": "self",
  "uri": "http://www.xyz.org/pdf/0123456789"
}

{
  "href": "https://registry.sdmx.org/ws/rest/dataflow/ECB.DISS/BSI_PUB/1.0",
  "rel": "dataflow",
  "urn": "urn:sdmx:org.sdmx.infomodel.datastructure.dataflow=ECB.DISS:BSI_PUB(1.0)"
}

{
  "href": "https://registry.sdmx.org/FusionRegistry/ws/rest/provisionagreement/ESTAT/PA_NAMAIN_IDC_N",
  "rel": "provisionagreement"
}

{
  "href": "https://registry.sdmx.org/help.html",
  "rel": "help",
  "title": "Documentation about the SDMX Global Registry",
  "titles": { "en": "Documentation about the SDMX Global Registry" },
  "type": "text/html",
  "hreflang": "en"
}

Collections of links can be attached to various elements in SDMX-JSON.

Similarly with standards such as HTML5 and Atom, link elements in SDMX-JSON must define a URL (the href attribute) and a semantic (the rel attribute). This allows clients to follow the links they care about and ignore the ones whose semantic they are not interested in. In addition, links in SDMX-JSON may define a title (a human-friendly description of the target link) and a type (a hint about the type of representation returned by the link). Please refer to the list of Media Types and Subtypes assigned and listed by the IANA for additional information about expected values for the type attribute.

SDMX-JSON offers a list of predefined semantics, but implementers are free to extend it. The list of predefined semantics comes from the list of SDMX artefacts that can be returned by SDMX RESTful web services, semantics defined in RFC5988 and additional items deemed to be useful in the context of statistical data dissemination. These semantics are:

  • SDMX artefacts: dataStructure, metadataStructure, categoryScheme, conceptScheme, codelist, hierarchicalCodelist, organisationScheme, agencyScheme, dataProviderScheme, dataConsumerScheme, organisationUnitScheme, dataflow, metadataflow, reportingTaxonomy, provisionAgreement, structureSet, process, categorisation, contentconstraint, attachmentconstraint, category, concept, code, organisation, agency, dataProvider, dataConsumer, organisationUnit, reportingCategory, Data
  • RFC5988: alternate, copyright, glossary, help, index.
  • Miscellaneous: calendar (link to a release calendar), source (information about the source of data), request (the SDMX RESTful query that triggered the SDMX-JSON response).

The URL captured in the href attribute can be absolute or relative. It is recommended to use absolute URLs in case the SDMX-JSON message is archived.