ISO/TS 19139:2007 Geographic information - Metadata - XML schema implementation
|Full name||ISO/TS 19139:2007, Geographic information – Metadata – XML schema implementation|
|Published by||ISO/TC 211|
|Online overview||Not yet available|
|Type of standard||ISO Technical Specification
|Related standard(s)||ISO 19109:2005, Geographic information - Rules for application schema|
ISO 19115:2003, Geographic information – Metadata
|Application||XML implementation of ISO 19115:2003, Geographic information – Metadata|
|Conformance classes||Constraints by-value or by-reference or gco:nilReason|
ISO/TS 19139:2007 defines Geographic MetaData XML (gmd) encoding, an XML schema implementation derived from ISO 19115.
This standard specifies the implementation of ISO 19115:2003, Geographic information – Metadata, in XML, using parts of GML, which is defined in ISO 19136:2007, Geographic information – Geography Markup Language (GML). In the same way that ISO 19115-1:2014 replaces ISO 19115:2003, while leaving a legacy of much metadata conforming to ISO 19115:2003, ISO/TS 19115-3, Geographic information – Metadata – Part 3: XML implementation of fundamentals (the XML implementation of ISO 19115-1:2014), will replace ISO 19139:2007 as the preferred XML schema implementation, but will not invalidate all the metadata already generated that conforms to ISO 19139:2007. ISO 19139:2007 also defines some general rules and is being revised to cater for them, and not the XML schema implementation of metadata.
The benefit of implementing ISO 19139:2007 will be to access all the metadata encoded using it, and until ISO 19115-3 has been published and implemented, to promote one’s products and services by providing one’s metadata to clearinghouses using ISO 19139:2007 for disseminating metadata.
However, this does not mean that the only way to implement ISO 19115:2003 is through XML, as defined in ISO 19139:2007. ISO 19115:2003 can be implemented in databases and GISs, and encoded using other markup languages such as JSON or GeoJSON, interchange formats such as ISO/IEC 8211 or ASN.1, or even as comma-separated values.
ISO 19139:2007 implements the metadata defined in ISO 19115:2003 through a collection of XML schema that conform to ISO 19118:2011, Geographic information – Encoding. Unsurprisingly, the standard requires a sound knowledge of XML to understand it. The reader also needs to understand ISO 19118.
Clause 5.2 specifies the namespaces used in this standard and clause 5.4 the UML model stereotypes. Clauses 6.1 to 6.8 provide brief overviews of the gmd namespace (geographic metadata extensible markup language), rule-based encoding, quality, web implementations, incorporating other existing XML schemas, multi-lingual support, polymorphism (supporting both multiple languages in the metadata and more detailed versions of metadata elements), and explaining how ISO 19139 conforms to ISO 19109:2005, Geographic information - Rules for application schema. Clause 7 describes how to implement extensions to the UML models, not so much for extensions to the metadata defined in ISO 19115:2003, but particularly for extending the CharacterString class to cater better for XML, including hyperlinks, URIs (uniform resource identifier) and file types; implementing multi-lingual free text and locales (language, country and character set) for text, which are not catered for in plain XML; transferring and aggregating datasets; and catalogues of coordinate reference systems, units of measure and code lists. Clause 8 provides details of how the encoding rules of ISO 19118:2001 have been implemented in ISO 19139:2007, particularly as ISO 19118 allows for multiple ways of transforming UML into XML. It covers the default XML Class Type encoding (a class is made up of one or more properties, such as attributes, associations, aggregations and compositions), XML Class Global Element encoding, XML Class Property Type encoding, special case encodings (abstract classes, inheritance, subclasses, enumerations, code lists, unions, metaclasses and externally identified implementations), XML namespace package encoding, and XML schema package encoding. Clause 9 provides the encoding descriptions, the relationships between the various namespaces used (gmx, gmd, gts, gss, gsr, gco), the organisation of the namespaces and their many XML Schema Definitions (XSDs) for all the metadata and other relevant packages, entities and elements defined in ISO 19115:2003 and other standards.
Annex B provides a data dictionary for extensions defined in clause 7, for web environment extensions, cultural and linguistic adaptability extensions, interchange or transfer, and code lists and enumerations. Annex C provides a brief summary of geographic metadata XML resources, specifically their URIs. Annex D provides implementation examples in XML. The actual XML defined in ISO 19139:2007 is provided in an online repository, rather than just printed out in the standard. The repository is maintained by ISO itself and caters for standards from a variety of ISO Technical Committees. See http://standards.iso.org/ittf/PubliclyAvailableStandards/ISO_19139_Schemas/ and http://standards.iso.org/iso/19139/.