Extending subject schemes

Robert and I are trying to work the items that are in draft comments
    in the 1.3 spec. We need help from the TC on the following draft
    comment (enclosed in a table below) in the "Extending subject
    schemes" topic:

    

    Extending subject schemes

    The <schemeref> element provides a mechanism for extending a
    subject scheme. This makes it possible to add

    new relationships to existing subjects and extend enumerations of
    controlled values.

    

    The <schemeref> element provides a reference to another
    subject scheme map. Typically, the referenced subject-scheme

    map defines a base set of controlled values that are extended by the
    current subject-scheme map. The

    values in the referenced subject-scheme map are merged with the
    values in the current subject-scheme map; the

    result is equivalent to specifying all of the values in a single
    subject scheme map.

    

    
      
        

          Comment by Kristen Eberlein on 5 February
              2015

            I added this topic to address comments made by Chris Nitchie
            in the targeted review. FYI, the paragraph above

            was in the DITA 1.2 Language Reference topic about
            <schemeref>.

            

            Re Example: Extending a subject scheme, Chris stated
            "That's not how keyref normally works. We

            definitely need normative language describing the expected
            processing of keyref in the context of a subject

            scheme. It's completely different from normal keyref
            behavior. Normally, a keyref is a reference to the content

            referenced by the key-defining topicref, not a reference to
            the topicref itself. And there's no transclusion or

            extension, as is implied here. So it's completely different
            processing rules for keys in a subject scheme, and it

            needs normative description."

            

            Re Example: Extending a subject scheme upwards, Chris
            stated " ... the use of keyref in subject schemes

            to recombine subject definitions is never covered anywhere."

            

            I suspect that we need additional normative content in this
            topic ...
        

      
    
    

    For the two referenced example topics, see the following:

    

    Example: Extending a subject scheme

https://td-demo.titaniasoftware.com/portals/ui/sample/viewer/5519e16ce4b016f565df9582/5519e185e4b016f565df9959/r/example-subjectScheme-extension

     Example: Extending a subject scheme upwards

https://td-demo.titaniasoftware.com/portals/ui/sample/viewer/5519e16ce4b016f565df9582/5519e185e4b016f565df9959/r/example-subjectScheme-extension-upwards.dita

    

    We either need to add normative content, or consider removing the
    example topics (which were present in 1.2). I don't know whether
    anyone is using this aspect of subjectScheme ...

    

    

    
-- 

      Best,

      Kris

      

      Kristen James Eberlein

      Chair, OASIS DITA Technical Committee

      Principal consultant, Eberlein Consulting

      www.eberleinconsulting.com

      +1 919 682-2290; kriseberlein (skype)