[topicmapmail] Are Facets Really Simple After All?

[Kal Ahmed]

On Sun, 2003-11-30 at 22:49, Murray Altheim wrote:
> Kal Ahmed wrote:
> > On Sun, 2003-11-30 at 18:32, Murray Altheim wrote:
> > <snip>
> > 
> >>   2. Using a Topic occurrence. I'm leaning towards advocating that
> >>      RDF-style property assignment be handled via Topic occurrences,
> >>      whenever the application doesn't demand or suggest they be
> >>      fully reified as Topics. There's some screwy semantics to doing
> >>      this that I'm not entirely comfortable with, as Topic occurrences
> >>      are occurrences of their Topics, not properties of their Topics.
> > 
> > Occurrences are "information that is specified as being relevant to a
> > given subject" (ISO 13250:2002, 3.28 - the same phrase is repeated in
> > XTM 1.0, section 2.2.3). I think it is a mistake to read too much into
> > the name "occurrences".
> Kal,
> 
> If I took that vague statement as the sum total of what we knew
> about Topic occurrences, I'd have given up long ago. If "information
> that is specified as being relevant to a given subject" were to only
> mean "relevant" as in "somehow connected" and not more explicitly
> "representative of" or "indicative of", then occurrences would be
> semantically meaningless or at best extremely vague, and essentially
> every Topic Map ontology would have "is relevant to" as its basic
> association type. In an ontology of medicine, military strategy,
> eBusiness, etc., basically *everything* "is relevant to" the overall
> subject.
> 
> My take on occurrences is that they are simply what they are called,
> occurrences of a Topic. There's enough vagueness in that statement
> alone to fly an airplane through -- expanding that to be anything
> relevant to a specific Topic means that every Association between
> two or more Topics is basically establishing relevancy, and the
> entire Topic Map would collapse. E.g., every one of the 700 Topics
> in my authoring ontology is somehow relevant to authoring, so I'd
> end up with one Topic with 700 occurrences. "is relevant to" is
> pretty useless. It's essentially a synonym for the most basic
> relationship: "is related to".
> 

You are welcome to do that if you want. However, you cannot expect that
the rest of the topic map user community will follow you. The definition
is vague, but if it has remained in both editions of ISO 13250 and in
XTM, you have to assume that it is vague for a reason.

However, you cannot state that "Topic occurrences are occurrences of
their topics", with reference to the standard, as the standard does not
say that.

> If we go back to the original idea of Topic Maps, as back-of-book
> indices, if one were to query the index for "description logics" in
> an index, nobody would expect to have returned say, the created date
> of the index entry itself. This is what you're suggesting is a valid
> use. I can't buy that could possibly be the intention of the standard,
> only that the text is vague. And we always interpret standards. The
> fact that both of us have been part of its development should inform
> us about a perhaps more correct interpretation than conflating the
> metadata about a Topic with its occurrences.
> 

Firstly, topic maps may have started as a BOTB index technology, but
that is not where they are now. Secondly ISO 13250 has been revised once
and this definition has not changed. Nor did it ever change in the time
the XTM 1.0 was being developed. So it seems to me that, up to now, the
standards committee has been satisfied with that definition.

Yes, you are free to make your own interpretation of the standard. But I
don't think that you can call the use of occurrences for storing meta
data a conflation unless you mean that as a criticism of the standard
rather than of the practice. 

>  > I have always considered it perfectly valid
>  > (indeed the only way) to encode properties of topics where the property
>  > value is not something that you want to talk about any further within
>  > the topic map.
> 
> That there is an inability to encode properties of Topics doesn't
> suggest that a form of markup abuse is permitted. The reason I
> started the thread on facets was to look into some sort of best
> practices for doing this kind of thing. Unless all of the vendors
> and developers were to agree upon some sort of PSI identifier (i.e.,
> something that really should be in the standard itself), we'd find
> applications displaying or using Topic metadata as if that were
> Topic occurrences.
> 

The discussion itself is useful if it is to help us distinguish
different types of "information relevant to a subject" and I encourage
that - indeed I have found this whole thread a very interesting one. My
only point is that you seemed to me to be implying that ISO 13250
constrains the use of occurrences in a way which from reading the
definitions I feel it clearly does not.

Cheers,

Kal
-- 
Kal Ahmed, Techquila
Standards-based Information Management
e: kal@techquila.com
w: www.techquila.com
p: +44 7968 529531