Vocabulary issues : relations, relationships, properties, patterns ... RE: [OEP] Draft of a note on n-ary relations

Natasha

I'm in the process of drafting a small annex to the note about representation of n-ary
relations in Topic Maps following Pattern 2, as you suggested I could have a try at it.

I stumbled on some vocabulary/conceptual issues in your document, so I wanted to figure
them out to make sure we will use the same words in the same meaning.

First issue is difference in use, if any, between "relation" and "relationship". This is
something I always had trouble with, even in casual language, and have been often
corrected by native english speakers. In my native French, there is a single word
"relation" that matches both - which does not help. In my background Mathematics land,
only "Relation" is used on a formal way, which makes things easy. You use both in the
document, and I don't figure in the context what are the difference in semantics, if any,
in using either one.

OTOH, Pat in a recent answer to this thread uses "relation-instance". This is
crystal-clear to me, and I buy the notion of relation as a class. In that case, and the
question goes to Pat as well, could a (specific) "relationship" be an instance of a
(generic) "relation"? So we would have "relationship" = "relation instance" ? This sounds
to good to be true. Or is it that "relation" has a formal definition, whereas
"relationship" is more casual in this context? Go figure.

If we stick to "relation-as-class", in the case of relation represented by a binary
property I agree with Pat we have to clarify the relationship (oops) between the relation
and the property, which are both classes. Are they equivalent classes? I would say no, but
... In the case of n-ary relations, in any case, it's clear that the relation is not a
property. But if we stick to the notion of the relation-as-class, what is the instance,
exactly, in Pattern 2? I think we have to clarify the difference between the individual
instance of Purchase and the instance of Purchase-Relation (which, IMO, would be difficult
to describe as a single OWL object).

In Topic Maps representation, things are clearer and cleaner for those matters.
Relation-classes are represented by association types, and relation-instances by
associations. So I have not much difficulty to represent and describe the situation in
Topic Map concepts and vocabulary, but I've hard time to figure which objects they map on
the OWL side.

And, last but not least, what does "pattern" capture exactly? What is the difference
between the relation-class and the relation pattern?

> It's nowhere near as complicated or as controversial (we hope) as the
> Classes as Values one. In fact, it's rather simple, almost too simple
> to be a pattern.

Do I complicate it on purpose? Are those issues to "sweep" also under the carpet (a bit
crowded down there)?

Cheers

Bernard

Bernard Vatant
Senior Consultant
Knowledge Engineering
Mondeca - www.mondeca.com
bernard.vatant@mondeca.com


> -----Message d'origine-----
> De : public-swbp-wg-request@w3.org
> [mailto:public-swbp-wg-request@w3.org]De la part de Natasha Noy
> Envoye : mercredi 5 mai 2004 03:16
> A : swbp
> Cc : Alan Rector
> Objet : [OEP] Draft of a note on n-ary relations
>
>
>
>
> People seem to have agreed that doing a pattern on n-ary (reified)
> relations would be a useful thing to have. Alan Rector and I actually
> had a chance to work it out and you can see the first draft  of our
> effort at
> http://lists.w3.org/Archives/Public/www-archive/2004May/att-0003/n-
> aryRelations.html
>
> It's nowhere near as complicated or as controversial (we hope) as the
> Classes as Values one. In fact, it's rather simple, almost too simple
> to be a pattern. On the other hand, it seems to be on a topic that many
> newcomers to OWL have questions on.
>
> As usual, please feel free to poke holes in it and all feedback is
> welcome.
>
> Thanks in advance,
>
> Natasha and Alan
>

Received on Wednesday, 12 May 2004 12:51:37 UTC