W3C home > Mailing lists > Public > www-rdf-logic@w3.org > June 2001

RE: definition/assertion (WAS rdf as a base for other languages)

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 12 Jun 2001 10:14:51 -0500
Message-Id: <v04210100b74bdb62de7e@[]>
To: "Ziv Hellman" <ziv@unicorn.com>
Cc: www-rdf-logic@w3.org
> > > a triple connecting a parent with a child, in a 
>subject-predicate-object format of person-parentOf-child, leaves 
>much unsaid -- a parent may
> > > have several children. If predicates serve as functions, then 
>this "function" might not have a well-defined value precisely 
>because the value
> > > could be any of a number of children. Of course one could make 
>the object a list, but that too has drawbacks. Logic long ago 
>handled >
> > > these matters by distinguishing between relations and 
>functions. But because relations can be multi-placed and do not 
>always fall neatly >
> > > into the subject-predicate-object framework, they are anathema 
>to many, to the detriment of the representational tools.
> > To be fair to RDF, I think itis based on the relational intepretation.
>A quick glance at the RDF spec shows you are probably right. Point 
>taken. But then I wonder how one could distinguish a relation from a 
>well-defined function in RDF ...

You can't in RDF, as far as I can tell, since it has no notion of 
equality. You can in DAML, with some awkwardness, by defining it as a 
property (= binary relation) with a uniqueness condition.

Pat Hayes

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Received on Tuesday, 12 June 2001 11:15:02 UTC

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