[sc34wg3] occurrence - basename fuzzy boarder

[Murray Altheim]

Geir Ove 翽 wrote:
> This thread is a bit old, but there is an issue I believe we never
> really resolved:
> 
>   "Should occurrences have variants?"
> 
> I think they should. The argument is that occurrences reference
> information resources, and that they can have alternative renditions
> applicable in different contexts. 

The information resources are occurrences of topics; if you are
trying to make statements about them, such as what *kind* of
resource they are, or how they're relevant to the topic in question,
that mechanism already exists in XTM.

> Examples: 
> 
>   - images in various resolutions (e.g. thumbnails)
>   - monochrome vs. color images
>   - documents in different formats (e.g. PDF vs. HTML), 
>   - reversed sound
>   - text written in different languages etc.
>   - sort keys (e.g. chronological)
 >
> What are the arguments for them _not_ having variants?

I don't see that any of these can't be supported within the
current syntax, if you stop calling these "variants", which
is simply a name we came up with for base name variants, not
to be taken as any kind of doctrine for topic maps generally.

In general, what you're calling occurrence variants can be
handled in XTM using <instanceOf> to define the class(es)
to which the occurrence belongs, or <scope> to specify the
context in which the resource is relevant to the topic. This
is perfectly appropriate and different from the use of
these elements elsewhere within <topic>. They are there
precisely to handle the kinds of things you cite in your
examples, except I believe "sort keys" which are to my mind
(unless I'm misunderstanding your usage) part of the topic
name and supported by the sort PSI, used as a variant on
base name.

Indeed, part of the reason I have been working on an XSD
datatypes-in-XTM topic map is to begin to define a set of
PSIs suitable for characterizing topic occurrences, eg.,

    <topic id="xx">
      ...
      <occurrence>
        <instanceOf>
          <resourceRef xlink:href="PSI_for_PDF"/>
        </instanceOf>
        <resourceRef xlink:href="http://www.foo.com/doc/article.pdf"/>
      <occurrence>
    </topic>

The other thing I suppose you could do if necessary is to
reify the occurrences as topics in their own right if you
want to make more complex assertions about them as resources.

Murray

......................................................................
Murray Altheim                  <http://kmi.open.ac.uk/people/murray/>
Knowledge Media Institute
The Open University, Milton Keynes, Bucks, MK7 6AA, UK

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