[sc34wg3] Issue xtm-def-occurrence-type

[Lars Marius Garshol]

(This is the first thread in what is likely to become a large number
of such threads on this list. The idea is to start with a small issue
that the Barcelona meeting is unlikely to bother with.)

In the current SAM document occurrence items either have a topic item
in their [occurrence type] property, or, if no occurrence type is
explicitly provided, the property is null.

XTM 1.0, on the other hand, says:

  "The default occurrence type is defined by the 'occurrence'
  published subject." (2.2.3)

  "The core concept of occurrence; the generic class to which all
  occurrences belong unless otherwise specified." (2.3.2)

The question is whether the approach taken by the current SAM is
compatible with that chosen by XTM 1.0. If someone were to write

  <occurrence>
    <instanceOf>
      <subjectIndicatorRef xlink:href="http://www.topicmaps.org/xtm/1.0/core.xtm#occurrence"/>
    </instanceOf>
    <resourceData>...</resourceData>
  </occurrence>

they would end up with an occurrence item that is different from what
they get if they write

  <occurrence>
    <resourceData>...</resourceData>
  </occurrence>

and the result of that is most likely that querying and constraining
these two occurrences would be done differently in TMQL and TMCL.
Their representation when deserialized is also likely to be different.

Is this acceptable? Can we live with this? Opinions on this are very
much wanted.

-- 
Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
ISO SC34/WG3, OASIS GeoLang TC        <URL: http://www.garshol.priv.no >