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

Re: Question: DAML cardinality restrictions

From: David Allsopp <dallsopp@signal.dera.gov.uk>
Date: Wed, 04 Apr 2001 09:55:29 +0100
Message-ID: <3ACAE181.9D380501@signal.dera.gov.uk>
To: pat hayes <phayes@ai.uwf.edu>
CC: www-rdf-logic@w3.org

pat hayes wrote:

> >OK. What if the data say that someone has two fathers? (for the sake of
> >argument, I receive an RDF message where the person's Resource has two
> >Father properties).  Presumably we must reject this message as logically
> >inconsistent?
> No, since it is not logically inconsistent. In fact it is not even
> legally inconsistent, given the adoption and inheritance laws.

> If you believe that fathers are unique you can say so, and then the
> conclusion would be that these two fathers were one and the same. If
> some other source denies this (for example, if you are assuming a
> unique names regime), you have indeed found a logical contradiction.
> All of these shouldn't be built into the logic, however, as there are
> people who work by different rules in all of these cases.

I've had two different replies to this question; our conclusion will
depend on what rules we use, as you say, but we won't have a complete
description of most real domains; some rules will be missing, so I'm
unsure what behaviour would be regarded as 'default' (or if there is no
such thing) in the situation above...

> >I take your point about representation, but at some point, to make
> >use of our data, we will often have to leave the logical
> >representations;
> >most software does not use FOL or anything like it, and probably never
> >will.
> You couldn't be more wrong.
> Concrete data IS logic, just a narrow subset of it.

Very well; the point remains unchanged, I believe; richer
representations will often need to be mapped into less rich
representations; this is perhaps not very interesting for the logicians
(or perhaps it is?), but it is of great importance to developers who
need to bring the functionality of 'legacy' applications onto the
semantic web.


David Allsopp.

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Received on Wednesday, 4 April 2001 04:59:31 UTC

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