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Proposal to close issue 5.21

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 18 Oct 2002 13:41:58 -0400 (EDT)
Message-Id: <20021018.134158.123574411.pfps@research.bell-labs.com>
To: jjc@hpl.hp.com
Cc: www-webont-wg@w3.org

From: Jeremy Carroll <jjc@hpl.hp.com>
Subject: Minutes: telecon 17Oct 02
Date: Fri, 18 Oct 2002 18:32:11 +0200

[...]

> ACTION: Peter to generate test case to show disjointUnionOf can be 
> rephrased w/existing constructs [and propose to close 5.21 by 
> removing disjointUnionOf]

[...]

As stated by Mike Dean in the description of Issue 5.21:

> owl:disjointUnionOf is an awkward construct (compared to rdfs:subClassOf)
> for many tools to support. It can be expressed using combinations of
> owl:unionOf or rdfs:subClassOf and owl:disjointWith (though perhaps without
> conveying the notion of providing a covering set when owl:disjointUnionOf
> is used with with owl:sameClassAs). I and other users of DAML+OIL recommend
> that we drop owl:disjointUnionOf from the OWL language.  

To further this,
	_:x owl:disjointUnionOf [_:d1 ... _:dn] .
has the same meaning (ignoring the RDF triples that arise from the syntax) as
	_:x owl:unionOf [_:d1 ... _:dn] .
	_:di owl:disjointWith _:dj . 		1<=i<j<=n

The only thing going for owl:disjointUnionOf is that it uses fewer triples
than the alternative.  However almost all disjoint unions are small so the
number of owl:disjointWith triples will not be that large.

Further, disjointUnionOf is *not* a disjoint union, as disjoint unions
do not force the disjointness of the components, instead differentiating
between them in the union.

For these reasons, I propose that owl:disjointUnionOf be removed from OWL,
and that wording be added to the reference manual to document the change
from DAML+OIL.

Peter F. Patel-Schneider
Bell Labs Research
Received on Friday, 18 October 2002 13:42:09 GMT

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