[topicmapmail] Are Facets Really Simple After All?

[Kal Ahmed]

On Mon, 2003-12-01 at 14:31, Murray Altheim wrote:
> Kal Ahmed wrote:
> > On Mon, 2003-12-01 at 00:24, Murray Altheim wrote:
> [...]
> >>But by the same token, I think simply a pragmatic analysis of
> >>what you're proposing should suggest some best practices. By that
> >>I mean, a simple reading in English of what you're suggesting.
> >>I can understand that an occurrence of the Topic "Paris, France"
> >>might be a latitude/longitude for Paris, an important date in
> >>its history, a photograph of the Champs Elysees, etc. The standard
> >>rightfully doesn't constrain any of this kind of thing; it would
> >>make Topic Maps much less interesting and valuable. But I can't
> >>imagine that a "correct" occurrence of the Paris Topic would be
> >>"2003-11-23T11:34:55", "245,190", or "#bce033" (i.e., the creation
> >>date of the Topic in my application, the location of the Topic
> >>node in my TouchGraph visualization, or the colour of the displayed
> >>node, resp.). That just isn't right. Now, if I never planned to
> >>share that Topic Map with anyone, hell, I can do what I like*),
> >>but it doesn't *to me* express a correct interpretation of the
> >>standard. Even in the inimitable vagueness of its definition of
> >>"occurrence", a property of a Topic and an occurrence of a
> >>Topic simply aren't the same thing. Certainly not semantically.
> > 
> > In that case we agree. But you talk here of meta data for the topic (as
> > opposed to meta data regarding the subject) for the first time. I was
> > simply pointing out that subject meta data is valid "information
> > relevant to the subject". I would expect topic meta data to be expressed
> > as occurrences of another topic whose subject is the topic construct
> > that you are making the assertions about. 
> 
> No, not the first time. The first message of the thread I started
> on facets outlined two forms, Model A (the "RDF" model) and Model
> T (the "facet" model). Metadata about a topic is what I've been
> talking about all along. That's what RDF is: metadata about a
> single thing, a simple triple. The differentiation between "metadata
> about a Topic" and "metadata about a subject" I'm not making. 

I think you have to make that distinction. You talk about the colour or
time of creation of a topic, none of those things are properties of the
subject, they are properties of the topic that represents the subject.
You would not mean that "The time of creation of Paris is
2003-11-23T11:34:55", regardless of how you expressed it you would mean
that "The time of creation of the topic who's subject is Paris is
2003-11-23T11:34:55".

> I'm
> going to have to answer Bernard, but in my first glance he mentioned
> that Topics are binding points. I agree with that. The triples in
> Model A are properties attached to the Topic. I consider those
> different than occurrences attached to the Topic. Occurrences are
> a specialized Association in the model that have their own special
> semantics and a special syntax in XTM, the <occurrence> element. We
> never created a <facet> element, nor did we a <property> element.
> 

I thought I had understood you to say that the values of these
properties apply to the topic, not the subject, but now I'm not at all
clear on that. 

Is your <property> actually meta data about the topic (e.g. time of
creation of the topic, UI representation of the topic etc.)? If so, then
I agree with you that occurrences of the topic itself is not the way to
express this. If you're property is meta data regarding the subject
(i.e. meta data about Paris, not meta data about the topic representing
Paris), then I see no need for anything beyond occurrences and
associations to express this information. If you are saying that a
<property> is both of these things, then how do you propose to tell the
difference (how do I distinguish the creation date of the topic from the
creation date of the subject that the topic represents ?)

Cheers,

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