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Action-67 some examples on b-nodes issues and their impact on users

From: Jeff Z. Pan <jpan@csd.abdn.ac.uk>
Date: Tue, 22 Jan 2008 22:53:07 -0000 (GMT)
Message-ID: <1113.87.113.90.116.1201042387.squirrel@www.csd.abdn.ac.uk>
To: public-owl-wg@w3.org


>Action 67: Jeff to lead effort on formulating some examples on
b-nodes issues and their impact on users

As Boris pointed out in the telecon, there was already a nice
example (hidden behind some rather technical discussions) in his
earlier email:

http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0177.html


In short, there are two choices for semantics of anonymous
individuals (b-nodes):

1) existentially quantified variables

2) skolem constants

Example:

Given an ontology O about friends (suppose there are no anonymous
individuals in O). Let us consider the following extra individual
axioms (where :_1 is an anonymous individual):

hasFriend(Bob,:_1)
hasAge(:_1,"26"^^xsd:integer)

With both semantics, the axioms both roughly say "Bob has some
friend aged 26" with some subtle difference: under semantics 1),
the friend aged 26 could be someone already mentioned in O, while
under semantics 2), the friend is someone new and cannot be
someone mentioned in O.

(The above is true unless we have some further extra axioms
forcing :_1 to be the same as some known individuals.)

Comments/Further examples are welcome.

Jeff
Received on Tuesday, 22 January 2008 22:53:34 GMT

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