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DTTF: How unasserted triples help

From: Jonathan Borden <jonathan@openhealth.org>
Date: Wed, 22 May 2002 15:38:23 -0400
Message-ID: <005d01c201c8$3d1a0e80$0a2e249b@nemc.org>
To: "WebOnt WG" <www-webont-wg@w3.org>
Cc: "Dan Connolly" <connolly@w3.org>
DanC raises the important question of how unasserted triples help OWL's
problem.

http://lists.w3.org/Archives/Public/www-webont-wg/2002May/0177.html

My impression is that since certain triples are unasserted by the RDF MT,
the OWL MT or axiomatic semantics etc. would be "free" to assert its own
meaning. For example

First using "asserted" triples, the following:

intersectionOf( student, employee ) or in N3

_:c1 rdf:type owl:Class
_:c1 owl:intersectionOf _:L1
_:L1 rdf:type owl:List
_:L1 owl:first <#student>
_:L1 owl:rest _:L2
_:L2 rdf:type owl:List
_:L2 owl:first <#employee>
_:L2 owl:rest owl:nil

which roughly translates to: "There exists a class having the intersectionOf
property whose object is a List, whose first element is #student and whose
rest is another List whose first element is #employee and whose rest is nil"

As "asserted" triples, these statements are said to be _truths_, which is a
bit strange because this isn't what we really mean. Instead we mean to say:

"There exists a class which is the intersectionOf #student and #employee."

So presumably the OWL MT would have a statement or axiom or something to the
effect that:

"intersectionOf(a , b) <=> intersectionOf( b, a)"

In this way, having _unasserted_ triples allows the OWL MT to apply its own
semantics to the triples (which we are using as syntax). The answer is that
having unasserted triples:

1) prevents paradoxes
2) allows the OWL MT to do its job of defining semantics for OWL statements

other examples would be

owl:import

etc. etc.

the idea being not that these statements would be lacking semantics, rather
that the truths stated in these OWL statements would be defined by the OWL
MT i.e.

"If it is true that John is a member of the intersectionOf(student,
employee) then it necessarily follows that John is a member of the
intersectionOf(employee,student)"

Problem solved, etcetera.

Jonathan
Received on Wednesday, 22 May 2002 15:42:51 GMT

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