[sc34wg3] Why is TMDM datatype not a topic?

Lars Marius Garshol sc34wg3@isotopicmaps.org
Fri, 30 Sep 2005 12:53:53 +0200

* Lars Heuer
| A bit late but I think this was not discussed here.
| Why is the datatype of an occurrence / variant not a topic? IMO the
| URI that is used to identify the datatype can be used as subject
| identifier.
| So, I'm curious why the datatype was modeled as simple URI and not
| as topic with the subject identifier <URI>.

The datatype is identified by a URI, and the URI is considered a
subject identifier. The rationale is that quite obviously the datatype
is a subject, and if we have a URI identifying it, well, what else
could that URI be?

Making the datatype a topic, however, has consequences, because what
then happens if someone adds this fragment to the topic map?

  <topic id="bang">

That would suddenly make all external and internal occurrences have
the same datatype...

This is why we stopped at subject identifier, and make it clear that
you can create a topic reifying the datatype, but if you then merge
those topics it has no impact on processing. This seemed the safest

I hope this answers your question.

Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
GSM: +47 98 21 55 50                  <URL: http://www.garshol.priv.no >