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Re: another revision of semantics document

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 21 Aug 2002 07:07:45 -0400
To: phayes@ai.uwf.edu
Cc: www-webont-wg@w3.org
Message-Id: <20020821070745Z.pfps@research.bell-labs.com>

Again, as far as I can see

	John rdf:type Student .
	John rdf:type Employee .

does not entail

	John rdf:type _:w .
	_:w owl:intersectionOf _:l1 .
	_:l1 owl:first Student .
	_:l1 owl:rest _:l2 .
	_:l2 owl:first Employee .
	_:l2 owl:rest owl:nil .

because there is no requirement that there be an element of the domain of
discourse whose class extension is the intersection of Student and
Employee.

For example, the following is a GHOWL interpretation of the premise

	S = { j, x, y, t, s, e } + other built-ins + sequence

	I(John) = j
	I(rdf:type) = t
	I(Student) = s
	I(Employee) = e

	ICEXT(Student) = { j, x }
	ICEXT(Employee) = { j, y }
	plus built-in class extensions

	builtin in property extensions

This interpretation is *not* an interpretation of the consequent, because
there is no class in the interpretation whose extension is { j }, and thus
there is no <x,S([Student,Employee])> in IEXT(I(owl:intersectionOf)).

Peter F. Patel-Schneider
Bell Labs Research
Received on Wednesday, 21 August 2002 07:07:55 GMT

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