Re: comment on N-ary relations draft

All

Guus has said it more clearly than I could of.  The issue is modelling rather
than logical structure.  

Another point is that it is common in the evolution of an ontology to start by
using a simple property plus binary relation and then move to pattern 1 -
re-representing the property as a class - as it becomes clear that an n-ary
relation is needed in at least some cases.  This is a common enough operation
that we are implementing a "wizard" to make it easier, either for a single
property or a whole group of properties.  

Often it happens that there is a large set of properties/cases that one wishes
to model consistently.  In this case, if any of the cases needs to be modelled
with pattern 1, then they all do.  Otherwise, modellers become hopeless confused
as to which conceptual relationship is to be modelled in which way.  

Finally, version 1 matches to ontological notion of a "quality" and "quality
space" as in Guarino and Welty's work, whereas this consideration is not
relevant to pattern 2.

Regards

Alan


Guus Schreiber wrote:
> 
> Peter F. Patel-Schneider wrote:
> 
> > I just read the N-ary relations draft and I am somewhat confused as to why
> > it has the two representation patterns.  I don't see that the two patterns
> > are different in any substantial way as the only difference between them is
> > the direction of one arrow.  This difference may matter in some formalisms
> > but doesn't in RDF/RDFS (as they are too weak to notice much difference) or
> > OWL (as it has the inverse construct).
> >
> > So, my question is why maintain the two different representation patterns?
> 
> Peter, thanks very much for the comment.
> 
> Natasha and Alan are probably the best people to answer this, but I will
> give you my reading of the difference.
> 
> The distinction is of a modelling nature. In Pattern 1 you create a
> helper relation (represented as a class) which has (in most cases) no
> name in the domain of interest. In Pattern 2 the relation class has some
> name in the domain, typically a noun representing some activity (e.g.
> purchase, enrolment, transaction, subscription). I think this is an
> important difference of which developers should be aware. In particular,
> in the case of pattern 1 a an engineer might find it weird to construct
> a name from the blue, and it may help her/him to know it's actually good
> practice. The resulting representation is very similar, I agree. Maybe
> we should make this point more clear in the text.
> 
> Hope this helps,
> Guus
> 
> Guus
> 
> >
> > Peter F. Patel-Schneider
> > Bell Labs Research
> >
> 
> --
> Free University Amsterdam, Computer Science
> De Boelelaan 1081a, 1081 HV Amsterdam, The Netherlands
> Tel: +31 20 444 7739/7718
> E-mail: schreiber@cs.vu.nl
> Home page: http://www.cs.vu.nl/~guus/

-- 
Alan L Rector
Professor of Medical Informatics
Department of Computer Science
University of Manchester
Manchester M13 9PL, UK
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Received on Wednesday, 8 December 2004 09:33:03 UTC