[topicmapmail] Are Facets Really Simple After All?

[Murray Altheim]

Kal Ahmed wrote:
> On Mon, 2003-12-01 at 15:31, Murray Altheim wrote:
[...]
>>I think my hesitancy is about the middle area. I think that the
>>definition of "metadata" is really what's more in question. What is
>>meta at one level isn't at another, and perhaps I'm simply trying
>>to tackle more than is necessary. In my original note the idea of
>>"Model A":
>>
>>   http://www.infoloom.com/pipermail/topicmapmail/2003q4/005406.html
>>
>>there is an attempt to "do" RDF, i.e., create a way in XTM to express
>>the simple triples of RDF. What *is* metadata? I dunno.
> 
> You are absolutely right, of course. What is meta data for some is
> information for others, its a matter of perspective. To my mind we use
> meta data to assist in searching, describing and classifying the
> information that we really care about. Meta data is just information
> that helps us work with the information that we want to work with.
> Transferring that view to the topic map world. I would suggest that for
> the most part, the information that we really care about (within the
> domain of the topic map - I'm not discussing the resources that the
> topic map links to as occurrences here) are topics, and has to be topics
> because if we care about this information we are going to want to say
> something about it. Then what ever we consider to be meta data can be
> treated as either topics or occurrences - depending on whether or not we
> believe this information to be something that someone else using the
> same topic map will care about enough to want to say something about.

I think we are in complete agreement.

>> But the idea
>>of being able to express simple triples about a Topic without invoking
>>the whole Topic machinery is what I have heard people yearn for since
>>we did XTM (and during its development). 
>
> Thats true. But I think that the occurrences mechanism we have is much
> more generally useful than simple triples.

Yes, but *perhaps* at the expense of what I've been calling semantic
violence. With only a slight flourish of Johnny Deppish piratese.

>>It's what we dropped when we
>>decided not to implement facets in XTM. 
> 
> Careful here. Facets in ISO 13250:2000 that did not make it into XTM 1.0
> are not properties of topics, they are properties of resources. You
> point to a resource and apply property value pairs to it. Sure, it could
> be a mechanism for providing topic meta data (by pointing to the topic
> element as the resource), but it was not principally created for that
> purpose. The reason facets didn't make it into XTM was that it was felt
> that if this resource is something you care about enough to want to
> attribute  property/value pairs to it, then you should create a topic
> that represents that resource and use occurrences. In other words, ISO
> 13250:2000 facets are a short cut for reification and using occurrences.

Ah, yes, an important and correct distinction, and of course the "R" in
RDF is for "resource".

I started to reply to your last sentence but then realized I was confused
by it. Are you saying that ISO 13250:2000 facets are neither Topics nor
occurrences? That they are something else, something not representable
in XTM? I'm not quite following. I suppose I'm still curious to know how
you'd "do" RDF in XTM, or if you'd not at all.

>>I think it might be dangerous
>>to attempt to distinguish between metadata about a Topic and metadata
>>about a subject for the same reasons that what is metadata at one level
>>isn't at another.
> 
> I have to disagree here. This is not a question of levels of detail in
> one domain, but two orthogonal domains. The domain being described by
> the topic map and the domain of topic map constructs. If you are not
> clear about that distinction, you end up assigning a DC:Creator property
> value to Paris meaning that you created the topic "Paris" but read by
> someone else to mean that you created the city of Paris.

Okay, fair enough.

>> All of this is likely very application-dependent, and
>>the approach taken in ISO 13250 (i.e., be very vague) could either be
>>considered a weakness or a strength.
>
> I would be very interested to see what kind of application could
> function properly without making a distinction between the domain being
> described (the territory) and the mechanics of its description (the
> map). Fortunately I think that ISO 13250 is abundantly clear that you
> cannot force those two things together in the occurrences construct -
> they are not for  information related to the topic construct, they are
> for information relevant to the subject.

No, I think you're on the money here. Me, just being unclear and fuzzy.

>>I've been going back and forth on this partly because the discussion
>>warrants it, and partly because I am somewhat sitting on the fence,
>>trying to figure which side would hurt the least if I fell off.
> 
> The only advice I can offer is to keep a strict separation between the
> map and the territory.

Well, given that that's advice I usually give, I can only agree. :-)

Murray

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

   International lawyers and anti-war campaigners reacted with
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