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Re: comparing DAML-ONT and OIL (was Re: semantics of daml)

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Mon, 16 Oct 2000 15:21:12 +0100 (BST)
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: connolly@w3.org, www-rdf-logic@w3.org
Message-ID: <14827.1907.580251.210553@localhost.localdomain>
On October 16, Peter F. Patel-Schneider writes:
> From: Dan Connolly <connolly@w3.org>
> Subject: Re: comparing DAML-ONT and OIL (was Re: semantics of daml)
> Date: Sat, 14 Oct 2000 22:59:58 -0500
> > I consider RDF to be always conjunctive; the suggestion
> > (in the RDF spec) that domain is disjunctive is
> > disputed; one of the RDF schema spec editors
> > agrees that it's bogus:
> 
> If DAML-ONT is going to use stuff from RDF that is suspect in some way,
> then there should be comments in the DAML-ONT document to the effect that
> either
> 1/ DAML-ONT will not use RDF in a way that will trigger the suspect
> behaviour
> or
> 2/ DAML-ONT depends on a change to RDF
> By the way, the most-recent RDF specification has no hint that domain will
> be changed.

I strongly agree. While I would also like to see some "sensible"
changes to the RDFS specification, we can't just assume our own
favourite changes when defining a language on top of RDFS - not if we
take the "ontology layer on top of RDFS" idea seriously. With OIL, the
approach taken was to live for now with the restrictions and
infelicities of RDFS, even though they complicate some of the OIL RDFS
syntax, while at the same time pressing for some changes to RDFS.

> > >   Individuals                   yes                     yes
> > 
> > I'm not sure I understand what Individuals are; cf
> > "universe of discourse" above.
> 
> Individuals are, well, individuals.  Things like Joe and Mary and a rock.
> Some systems only allow classes.  There are lots of related issues, such as
> whether a class is also an individual, and whether there are things like
> metaclasses.  

Given a denotational semantics that interprets a class as a set of
objects, then an individual is interpreted as a single object. A
unique name assumption is often made (i.e., different individual names
must denote different objects), and in this case we can "abuse
notation" by confusing individuals with the object they denote - so a
class can be seen as denoting a set of individuals, and an individual
as an element in the interpretation of a class.

Ian
Received on Monday, 16 October 2000 10:40:32 GMT

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