Re: [topicmaps-comment] TAO vs. ERA

[Lars Marius Garshol <larsga@garshol.priv.no>]

* Robert Barta
| 
| In the introductory papers I often read that 'instanceOf' is a
| special association

That's correct. XTM 1.0 is actually quite explicit about this.  An
<instanceOf> element is equivalent to an instance-of association with
no scope. (See annex F.3.2 of XTM 1.0. The infoset model garbles this
somewhat, and that's an issue we'll have to tackle at some point.)

This design decision was actually documented:

<URL: http://www.doctypes.org/xtm/syntax/Ontopia-syntax-comments.html#TOPIC >

| and a shorthand form for
| 
| (is-specialisation-of)
| specialisation: my-thing
| general-thing: my-class

Not "specialization of", but "instance of". Specialization is the same
as subclassing, which is something else entirely.
 
| For associations I can choose a scope to constrain its validity,
| for instanceOf I can not. In other words, the scope of an instanceOf
| is then the unconstrained-scope? 

Exactly!

| Do I interpret something into the standard which is not here?

No, you're following its express intent.
 
* Lars Marius Garshol
|
| Doesn't that match how we use the topic in a topic map? Composer is a
| concept. You can be an instance of it, or you can play it in relation
| to a piece of music. I being useful as a role does not stop you from
| being used for other things.
 
* Robert Barta
|
| Really? The type 'composer' is as you said earlier 'socially
| accepted as concept'. Here we are thinking about people playing
| some instrument and denoting the tune of songs, operas, musicals...
| 
| Playing the role 'composer' in an association is different to me, 
| in a subtle sense. Here it is only relevant in the context of the
| association:
| 
| (composes)
| composer: roger-waters
| album: the-wall

I agree, but I think that has to do with the use of the concept,
rather than the concept itself. I think the quote Tom Passin posted,
by John Sowa, really explained this extraordinarily well.

--Lars M.