Re: [xtm-wg] Whatever happened to facets?

["Thomas B. Passin" <tpassin@home.com>]

[Steve Pepper]

> At 17:49 29.04.2001 -0400, Thomas B. Passin wrote:
> >So that's what happened to facets!  They were replaced by unary
> >associations.  I always wondered.
>
> Well, no, not quite...
>  ....

> After the event, it turned out that facets were underspecified, ...

[Tom]
I did think that facet links were an unusual way to represent properties.
That was because the facet values for a particular kind of property were all
gathered together somewhere removed from the topics they appied to,
connected by a reference.  Very different from one's usual way of thinking,
which is more like RDF's triples.  On the other hand, once you got used to
it, facetlinks were a fairly compact way to list properties.  You could use
the data: URI scheme to fake around the problem of needing an addressable
facetvalue, although that might not have been understood by all processors.

[Steve]
> and that there were a number of misconceptions about how they
> should be used.
>
I noticed that several apps that used an xml version of 13250 didn't
interoperate where facets were concerned.  They wanted something a little
different from each other.

[Steve]
> So there was already considerable disgruntlement with facets
> by the time XTM was put on the agenda.
>  ...
>
> Now, since a resource *is* an addressable subject, it is easy
> to reify it as a topic. Once that is done, it can be assigned
> characteristics, including property-value pairs. This could be
> done either through occurrences or associations (which amount
> to basically the same thing, since another insight of the XTM
> process revealed that occurrences were in fact just a special
> kind of association).
>

[Tom]
I always had trouble understanding the text talking about occurrances in
13250.  What were they supposed to be that was different from a facet, for
instance?  I read it as saying that information "about" a particular topic
"occurs" at some URI, and that you de-reference (retrieve) the URI to find
out what the information actually contains.

Now the XTM spec has simplified the language and I can understand the intent
better.

> The details of the mapping between 13250 facets and XTM
> constructs has not been worked out in detail, and certainly
> not specified anywhere. (I believe the foregoing explanation
> is the first time anyone has actually written up this stuff...)
> This needs to be done and it is one of the aspects of the
> relationship between 13250 and XTM that will be addressed at
> the upcoming SC34 meeting in Berlin.
>
> So, Thomas, you were close. Facets *did* get replaced by
> associations, but those associations need not be unary, and
> they could also be occurrences.
>
[Tom]
:-)

> Hope this helps.

[Tom]
Yes, thanks very much, Steve.

Regards,

Tom P


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