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classes as instances (was Re: comments on RDF mapping)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 02 Nov 2007 08:34:35 -0400 (EDT)
Message-Id: <20071102.083435.235670726.pfps@research.bell-labs.com>
To: jjc@hpl.hp.com
Cc: public-owl-wg@w3.org

There was quite a bit of discussion in the WebOnt WG on
classes-as-instances, including the following exchange.  (I have added
an attribution to the message.)

peter


[http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0183.html]

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Fri, 25 Oct 2002 14:33:47 +0200
Subject: Re: Issue 5.19 Classes-as-instances
To: "Ian Horrocks" <horrocks@cs.man.ac.uk>,
    "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
Cc: <www-webont-wg@w3.org>

[ On October 18, Jeremy Carroll writes: ]

> > Description: (informative)
> >
> > If two URIrefs denote the same thing, then their class
> extensions are also
> > the same.
> >
> >
> > premises
> > ========
> >
> > first:thing owl:sameInstanceAs first:sameThing .
> >
> > conclusions
> > ===========
> >
> > first:thing owl:sameClassAs first:sameThing .
> >
> >

Ian:
> Name separation is not an inherent requirement of Fast OWL, and is not
> enforced in the abstract syntax - individuals and classes can have the
> same names, but are not logically connected.
>
> Name separation is required, however, if Fast OWL is to be embedded in
> RDFS in such a way as to be semantically compatible with Large OWL.
>
> Ian
>

One way of moving forward would then be to allow classes-as-instances in
all OWLs but to make (large owl) entailments that relate the two (like
this test case) not a Fast OWL requirement (and hence not an OWL Lite
requirement).

Jeremy



From: Jeremy Carroll <jjc@hpl.hp.com>
Subject: Re: comments on RDF mapping
Date: Mon, 29 Oct 2007 18:00:08 +0000

> I think the best way to address punning is by stating the requirement 
> and looking at whether:
> 
> a) this requirement is a requirement, and how widespread
> b) whether punning meets this requirement
> 
> The only articualtion of the requirement that I am familiar with is:
> 
> http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.19-Classes-as-instances
> 
> During the earlier group I felt that it was understood that the 
> requirement was not just that you could use the same name for a class as 
> for an instance, but that some logical consequences would follow.
> 
> for example
> http://www.w3.org/TR/owl-test/byFunction#sameAs-001
> 
> This is an OWL 1.0 Full entailment, which (perhaps with minor syntactic 
> change) would become an OWL 1.1 DL non-entailment (if I have understood 
> punning semantics correctly).
> 
> This seems like a divergence away from OWL 1.0 balance between Full and 
> DL, and also a divergence away from what I believe the requirement of 
> classes as instances is. If two items are the same instance, then they 
> are necessarily the same class.
> 
> The tests that I think express the punning issue are:
> 
> 
> <a> owl:sameAs <b>
> 
> entails
> 
> <a> owl:equivalentClass <b>
> 
> 
> and
> 
> 
> <a> owl:sameAs <b>
> 
> entails
> 
> <a> owl:equivalentProperty <b>
> 
> 
> I currently believe that the member submission OWL 1.1 semantics has 
> these both as non-entailments, and that a requirements doc for the use 
> case of using an instance URI as a class URI or an instance URI as a 
> property URI would have these entailments as holding.
> 
> (Obviously it is possible to give a post hoc rationale in which these 
> entailments are unimportant - it is easier to tell whether or not a 
> design meets a requirement if the requirement is written down, before 
> the design is)
> 
> Since the OWL 1.0 design solves this problem, in the manner given by
> 
> http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.19-Classes-as-instances
> [[
> Part of OWL Full.
> ]]
> (and syntactically excluded from OWL DL)
> 
> I personally see a variation in which this becomes
> 
> "Part of OWL Full; syntactically permitted in OWL DL, but with weaker 
> semantics."
> 
> as a backward step
> 
> Jeremy
Received on Friday, 2 November 2007 12:45:27 GMT

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