[sc34wg3] Topic names and occurrences in the TMDM

Murray Altheim sc34wg3@isotopicmaps.org
Fri, 30 Sep 2005 10:55:57 +0100

Lars Marius Garshol wrote:
> * Jan Algermissen
> | 
> | Since TMDM suggested practice seems to be to express attributes of
> | subjects (age, height, eye-color, department number etc.) as
> | occurrences [...]
> This has been the practice in the Topic Maps community ever since XTM
> 1.0 was published in 2001, and was why internal occurrences were
> introduced in the first place. XTM 1.0 even contains an example of
> such use in 3.9.1:
>   <URL: http://www.topicmaps.org/xtm/1.0/#elt-occurrence >
> This is not a TMDM innovation.
> | Subject Indicators and Subject Address are then, BTW, also just
> | occurrences.
> No, they are not. TMDM is very clear that occurrences are statements
> about the subject, but these two are not. (And it's subject locator.)
> They are also structurally different (they cannot be scoped, and they
> cannot be reified).
> | I have allways wondered what the benefit of four constructs for
> | things that are just semantic variations of a basic functinality
> | could be....seems awkward to have to implement basically the same
> | thing four times....
> Who says you have to implement it four times? Your internal model can
> be simpler if you want it to be. Look at TMRM, or Q. The point is
> that, as Kal says, the *semantics* matter.

Lars Marius and Kal,

In looking over this discussion in retrospect, I think I was
thrown by the idea of Topic names and subject identity being
considered as Topic Occurrences, but I realized (rather quickly
upon reading Kal's message) that I've been using Occurrences as
containers for Topic properties in my own practice for a long
time, and indeed, have both implemented properties-as-occurrences
in Ceryle and designed the Facet PSI set and its implementation
as typed Occurrences.

So on the subject of using Occurrences (internal or external) as
a means of ontologically assigning properties to a Topic, I think
we're on the same page.

Thanks for the clarification,


Murray Altheim                          http://www.altheim.com/murray/
Strategic Services Development Manager
The Open University Library and Learning Resources Centre
The Open University, Milton Keynes, Bucks, MK7 6AA, UK               .

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