[sc34wg3] Use cases for occurrence variants

[Kal Ahmed]

Steve Pepper wrote:

> At 20:16 04.03.2003 -0800, 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:
>>
>> 1. Thumbnail(s) of an image.
>> 2. Description of an image (displayability).
>> 3. Alt text (displayability).
>> 4. Sorting occurrences (sortability).
>> 5. Alternate address depending on device context, protocol, etc.
>> 6. Model inconsistency between base names and occurrences.
>>
>> Any others?
>
>
> I think that pretty much covers it.
>
> #5. is perhaps the most important, so I would put it at the top and
> call it "Alternate renditions" rather than "Alternate address". It
> would include alternate notations, resolutions, sizes, etc. For
> example, in the XML Papers application, the PDF and HTML versions of
> a paper might be variant occurrences of the XML version.
>
> As someone who has been playing devil's advocate and didn't really
> want variant occurrences, your list scares me. What it tells me is
> that there is a whole range of very useful and necessary functionality
> we are excluded from using unless we are prepared to use associations
> instead of occurrences. (And even then we don't have an application-
> independent way of capturing the relationship between variant forms
> of a resource.)
>
> I would almost go as far as to say that without variants, occurrences
> are virtually useless. It surprises me that more people haven't thrown
> up their hands in despair. Maybe no-one is actually using topic maps?

Maybe they have just found other ways of expressing their models.

1 - 4 could all be handled by reification of the occurrence resource.

5 could be handled either by reification or by making use of facilities 
in the HTTP protocol for user agent identification.

Cheers,

Kal