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Assertion -v- inference

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Mon, 16 Oct 2000 13:45:21 +0100 (BST)
To: www-rdf-logic@w3.org
Message-ID: <14826.61657.542503.577864@localhost.localdomain>
We should be clear about the difference between assertion and
inference. It may be the case that, for a set of assertions S, x=y
w.r.t. S is a valid INFERENCE (this is trivially true if S contains
the ASSERTION "x=y"). Moreover, the fact that x=y is not a valid
inference w.r.t. S does not meant that x<>y is a valid inference, nor
does the fact that x=y is "true" (given some external definition of
truth) have any effect on these notions - in fact I have often
observed that in these kinds of discussion the use of "real world"
examples only serves to confuse the issue as we allow pre-conceived
ideas of truth and falsity to influence our thinking.

An assertion of the form x=y (or x->y), where x is a class/relation
name, is often called a definition (primitive definition) of x. This
seems to be a useful notion, as most realistic ontologies consist for
the most part of this kind of assertion. However, in the world in
which we are operating there could be any number of similar
assertions, as well as other assertions that would allow us to infer
additional information about x. In this framework, there is no clear
distinction between defined and primitive classes - we can only say
whether a given assertion is of the form x=y or x->y. In OIL,
"defined" simply means that the assertion is of the form x=y.

Ian Horrocks, Department of Computer Science,
University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Tel: +44 161 275 6133  Fax: +44 161 275 6204  Email: horrocks@cs.man.ac.uk
URL: http://www.cs.man.ac.uk/~horrocks
Received on Monday, 16 October 2000 09:07:45 UTC

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