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RE: AllDisjoint in RDF mapping

From: Swanson, Tim <tim.swanson@semanticarts.com>
Date: Fri, 23 Feb 2007 10:44:28 -0700
Message-ID: <51F1B258494D5A4488C95F40E55F35D52F3E68@exchsrvr.semanticarts.local>
To: <public-owl-dev@w3.org>

Jim Hendler Wrote:
> actually, I do have a little problem with disjointUnion - the problem
> is that this would be the first OWL feature (I think) that combines
> two definitions at the same time -- so if I say
> Class A == DisjointUnion (B,C,D)     (with the obvious meaning, no
> syntax implied)
> then I am asserting both the definition of Class A AND the fact that
> B,C, and D are disjoint.  From a human point of view, I wonder if it
> isn't better to avoid the syntactic sugar and have this remain as two
> assertions
> Class A= Union(B,C,D)
> AllDisjoint(B,C,D)
> just seems to me that the clarity in the modeling would be clearer
>   -JH

Although I'm not a regular contributor to this list, I have been
monitoring this discussion and feel compelled to agree with this. I've
been leery of disjointUnion from the start. The problem is that, in
making an assertion about one resource, I am making assertions about
others as well.

As I understand it, defining the class "A" as the disjointUnion of "B"
and "C" would cause a reasoner to infer that "B" and "C" are related
using the standard owl:disjointWith property. So that, with reasoning
turned on, anyone browsing this ontology would see the normal, OWL 1.0

However, if I am not using a reasoner (browsing the asserted ontology),
then I wouldn't see this disjointness unless I happened to look at the
definition of "A". This would make modeling difficult.

I realize that this is, in a technical sense, no different from any
other axiom that is inferred rather than asserted. But from a modeling
standpoint using the disjointUnion construct /is/ an assertion of
disjointness between "B" and "C". Most DL inferences are the result of
two or more asserted axioms. In this case, it's a direct implication of
one axiom based on another.

I'm starting to repeat myself so I'll sign off, but I just wanted to add
my vote to this debate.


Tim Swanson
Semantic Arts, Inc.
Fort Collins, CO
Received on Saturday, 24 February 2007 00:28:13 UTC

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