W3C home > Mailing lists > Public > www-rdf-logic@w3.org > February 2002

Re: Challenge for RDF Gurus :)

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Mon, 18 Feb 2002 18:31:59 -0600
Message-Id: <p0510140ab897498542e5@[65.212.118.219]>
To: tarod@softhome.net
Cc: www-rdf-logic@w3.org
>   Just for playing.
>
>   if you followed the mails between Brian McBride and I, you will know
>about the different semantics for range and domain properties.
>
>   His proposal is the official, mine is just what I think it should be
>(just me)
>
>   So, I wanted to propose to the 'gurus' a little challenge
>
>   Try to represent that in rdf schema
>
>   Class A
>   Class B
>
>   property c(range(A or B), domain(A and B))

I take it that this means that the range is the union and the domain 
is the intersection. The official answer is that you can't. What you 
can do is this:

_:x rdfs:range A .
_:x rdfs:subPropertyOf C .
_:y rdfs:range B .
_:y rdfs:subPropertyOf C .
C rdfs:domain A .
C rdfs:domain B .

This says that the domain is contained in A intersect B, and that the 
range is contained in a class containing both A and B. That's the 
best you can do in RDF since it doesn't have any kind of negation or 
'lower-bound' construct that could prevent a range or domain being 
smaller than stated.  If you want to be more exact about upper and 
lower bounds of classes, you will need to use a more expressive 
language, such as DAML.

Pat Hayes

PS. BTW, if you think of 'domain' and 'range' in terms of category 
theory, then you would expect multiple ranges to intersect and 
multiple domains to union. So learn to think about domains and ranges 
differently. RDF properties are not really like functors or mappings; 
they are really binary relations. The distinction between domain and 
range is just the distinction between first and second argument 
position, not a deep matter. So one would expect them to at least go 
the same way under multiple assertions, and intersecting them is the 
natural way to go since RDF triples are basically conjoined rather 
than disjoined in an RDF graph.


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Received on Monday, 18 February 2002 19:31:50 GMT

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