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Re: Proposal to close issue 5.21

From: Dan Connolly <connolly@w3.org>
Date: 23 Oct 2002 14:18:54 -0500
To: "Peter F. "Patel-Schneider <pfps@research.bell-labs.com>
Cc: jjc@hpl.hp.com, www-webont-wg@w3.org
Message-Id: <1035400734.10068.7520.camel@dirk>

On Fri, 2002-10-18 at 12:41, Peter F. Patel-Schneider wrote:
> 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

That's pretty much what I was looking for, but
I'd like to see it go into the guide, in
a slightly more concrete form, ala...

Suppose you want to represent a class 'natural thing',
which is either animal, vegetable, or mineral.
You can express this ala:

	:NaturalThing rdfs:label "natural thing";
		owl:unionOf (:Animal :Vegetable :Mineral). *

Now while we know that nothing is both an animal and
a vegetable, we haven't formalized that yet. Here's
how we do that:

	:Animal owl:disjointFrom :Vegetable, :Mineral.
	:Vegetable owl:disjointFrom :Mineral. **


*full RDF/xml:

<rdf:RDF xmlns="http://example/vocab#"

    <rdf:Description rdf:about="http://example/vocab#NaturalThing">
        <rdfs:label>natural thing</rdfs:label>
        <owl:unionOf rdf:parseType="Collection">
            <rdf:Description rdf:about="http://example/vocab#Animal"/>
            <rdf:Description rdf:about="http://example/vocab#Mineral"/>

perhaps more clear with some of the fiddly bits elided:

    <rdf:Description rdf:ID="NaturalThing">
        <rdfs:label>natural thing</rdfs:label>
        <owl:unionOf rdf:parseType="Collection">
            <rdf:Description rdf:about="#Animal"/>
            <rdf:Description rdf:about="#Vegetable"/>
            <rdf:Description rdf:about="#Mineral"/>

** full RDF/xml left as excercise to editor/reader.

You might find the online RDF/N3->RDF/XML converters handy:

or... hmm... you might find them lacking Collection support
and otherwise out of date or unavailable. :-{

> 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.

Actually, I researched that and found both uses of "disjoint union"
in use.

> 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.


Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Wednesday, 23 October 2002 15:18:51 UTC

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