[WCMP] conceptual "extension" encoded as restrictions in terms of XML

The WMO core metadata profile, version 1.3, says it is a restricted profile of ISO 19115:

A category-1 profile places additional restrictions on the use of an International Standard to meet the more specific requirements of a given community

But I found some people described it's an extended profile because it has additional codelists. Which is right?

In my view, both.

Apparently opposite terminologies reflect different levels of viewpoint: conceptual and concrete, or more frankly, UML and XML.



Let me begin with the concrete level, or XML structure.  There should be little chance of objection if I define "extension" and "restriction" in the XML structure by use of and in W3C XSD. We can learn following relationships:

• There exist some instances that validate against the extended XSD and don't validate against the base XSD
• All instances that validate against the restricted XSD always validate against the base XSD

More practically:

• New XML element or attribute has to be introduced by extension
• If a simple type element accepts only a limited set of values than in the base schema, that is restriction

Then we can translate the definition to the conceptual level or UML:

• New property has to be introduced by extension
• If a property accepts only a limited set of values than in the base standard, that is restriction

In the WCMP 1.3, we had requirements of new information.  For example, any metadata record must have at least one keyword coming from a controlled vocabulary which we called the codelist WMO_CategoryCode.

It might have been idealistic if we added the new information as the new property in the UML.  However, in 2008, the WMO expert team decided *not* to extend the XSD of ISO 19139 because of interoperability.  So the new codelists are expressed as the special keywords.

ISO's XSD has definition of keyword of course, and it allows any text as keyword text and thesaurus title.  WCMP 1.3 requires at least one descriptiveKeywords block must have "WMO_CategoryCode" as the title of the thesaurus and the keywrod text must be chosen from the specified list.   That is restriction in terms of XML technology, while it comes from added value, probably extension of conceptual model.