[sc34wg3] Use cases for occurrence variants

[Murray Altheim]

Nikita Ogievetsky wrote:
> To get occurrence variants discussion down to Earth
> I suggest that we try to summarize use cases.
> 
> Here are those that I know of or have seen mentioned so far:
> 
> Thumbnail(s) of an image.
> Description of an image (displayability).
> Alt text (displayability).
> Sorting occurrences (sortability).
> Alternate address depending on device context, protocol, etc.
> Model inconsistency between base names and occurrences.
> 
> Any others?

As I mentioned previously, Michel had seen the need for these and
proposed it originally in XTM 1.0, i.e., adding <baseName> to
<occurrence>. It was voted down for reasons of added complexity,
and lack of demonstrable need. Also (if I remember correctly)
because occurrences in the model didn't have names, only topics
did.

If we add <baseName> to <occurrence> one could then argue we should
likewise (for consistency' sake) add <baseName> to <association>
too.

The solution to my mind is still that if one considers an occurrence
as something to be talked about in its own right, to be sorted,
displayed, checked with other occurrences for uniqueness, etc.,
then the ID of the occurrence should be reified as a topic and
operated upon as any other topic. "Conveniences" in many instances
do not add convenience for all applications, only some subset. For
those other subsets, support for those "conveniences" amounts to
making applications quite a bit more complicated.

I for one do NOT want Topic Maps made any more complicated. We're
having a hard enough sell as it is without adding more complexity
and altering the language any more than is *absolutely* necessary,
certainly not for convenience' sake.

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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