Thanks, Adrian, I missed these posts you made to the RDF list: very good! (01)
By the way, do you have a copy/ptr to the "Complexity
and the Expressive Power of Logic Programming", paper of Voronkov, Dantsin,
Eiter and Gottlob? (02)
By the way, there is some fairly recent work on guarded quantification,
which is decidable, that folks might be interested in. So it's actually the
guarded fragment of FOL. (03)
Van Bentham's
http://www.folli.uva.nl/CD/1999/library/evening%20lectures/Van%20Benthem/ASL
-Utrecht.pdf. (04)
C. Areces, C. Monz, H. de Nivelle, M. de Rijke. The Guarded Fragment: ins
and outs. In: J. Gerbrandy et al., eds. JFAK. Essays dedicated to Johan Van
Benthem on the occasion of his 50th birthday. (see
http://turing.wins.uva.nl/#j50/cdrom). The paper is at
http://citeseer.nj.nec.com/431035.html (05)
The latter is an especially good paper, and relatively informal. (06)
Thanks,
Leo (07)
-----Original Message-----
From: Adrian Walker [mailto:adrianw@xxxxxxxx]
Sent: Sunday, February 22, 2004 2:12 PM
To: [ontolog-forum]
Cc: Franklin L Obrst
Subject: RE: [ontolog-forum] Frames vs Logic again (08)
Hi Leo -- (09)
Nice summary of some AI-type reasoning systems. (010)
It may also be of interest to see how far one can go in expressiveness
while insisting on decidability and termination. (011)
There was some discussion of this in the rdf-logic list a while back, see
e.g. (012)
http://lists.w3.org/Archives/Public/www-rdf-logic/2003May/att-0041/00-part (013)
http://lists.w3.org/Archives/Public/www-rdf-logic/2003Oct/0020.html (014)
Cheers, -- Adrian (015)
At 10:41 AM 2/22/04 -0500, you wrote:
>This is true of all frame systems that I know of, i.e., slots. Slots are
not
>really predicates or relations (which are for binary relations,
>bidirectional as Adam says), but instead are "directed". If the underlying
>OKBC model of Protégé supported n-ary "relations", it would still be the
>case that one argument is focused on, since frame systems are
>object-centered, and OKBC is a frame system. Yes, I would add inverse slots
>for all of these, if you use Protégé, indeed a duplication. In OO-like
>systems (like frame-based systems) slots are typically used for
>"attributes", and the inverse is usually not called out.
>
>More purely logic-based systems like KIF don't have this problem.
>Unfortunately, frame systems are kind of a relic from earlier, pre-logical
>AI, and in fact were created as alternatives to logic, not a good idea.
>
>Description logics (which seek less expressive logics in general than FOL
>[1], to enable more tractable automated reasoning) formalize and extend
>frame systems. In DLs, you'll find a different notion, i.e., roles, which
>muddy the situation a bit more, since roles are rather like slots. A good
>tutorial on Description Logics is Franconi's at:
>http://www.inf.unibz.it/~franconi/dl/course/.
>
>For a comparision of the various formalisms, see [2], off the above
>tutorial.
>
>[1] But some DLs are actually more expressive than FOL, e.g., if they allow
>for transitive closure (of roles) or fixpoints.
>[2] D. Nardi, U. Sattler, D. Calvanese, R. Molitor. Relationships with
>other formalisms. In the Description Logic Handbook, edited by F. Baader,
D.
>Calvanese, D.L. McGuinness, D. Nardi, P.F. Patel-Schneider, Cambridge
>University Press, 2002, pages 142-183.
>http://www.inf.unibz.it/~franconi/dl/course/dlhb/dlhb-04.pdf.
>
>Leo
>
>-----Original Message-----
>From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Patrick
Cassidy
>Sent: Saturday, February 21, 2004 11:58 AM
>To: [ontolog-forum]
>Subject: Re: [ontolog-forum] Frames vs Logic again
>
>
>Yes, hasName and several other concepts that neither add to nor detract
>from the logical content were added to take advantage of the visual
>representation capabilities of Protege. If they bother anyone, they
>can be sequestered in a separate module and left out of versions
>that don't get imported into Protege.
> It is also possible in Protege to create windows with lists
>of propositions where a given concept is in position 2 or 3 or whatever,
>just as the SUMO browser and Sevcenko's browser have done. But at
>this point I haven't implemented that, since that is already covered
>by the other browsers. It is not a built-in function in Protege.
>To cover that issue, I have only added a few inverse relations
>thus far for those cases where the presence of a
>concept as argument 2 in the SUMO relation can be of significance in
>understanding a concept. If it turns out that viewing relations with
>classes as argument 2 is of more general interest, I can create
>a separate pane for the Class window that displays such relations.
>
> Pat
>================
>
>Adam Pease wrote:
>
> > Pat,
> > I noticed in your file of suggested additions the following:
> >
> > --------------------------
> > (instance hasName BinaryRelation)
> > (domain hasName 1 Entity)
> > (domain hasName 2 SymbolicString)
> > (inverse hasName names)
> > (documentation hasName "hasName relates an instance of an entity to a
> > string of linguistic characters used to reference the entity in
> > linguistic communication. This is the inverse of the SUMO relation
> > 'names', added to allow more flexible representation in Protege. The
> > hasName relation is not a necessary relation since not every entity is
> > named by a SymbolicString and not every SymbolicString is the label for
> > an entity.")
> > ----------------------------
> >
> > This is entirely redundant with the existing SUMO relation 'names'. The
> > only reason one would want such a definition, is, as you note, to
> > overcome the limitations of a frame system. A frame system is oriented
> > to inspection and reasoning on the first argument, so if one looks at
> > the frame for 'SymbolicString' one won't see the slot 'names'. It will
> > only be visible when one is looking at the frame for 'Entity'.
> >
> > If you feel the need for this inverse of 'names' a case could be made
> > that every binary relation must also have an inverse, thus doubling
> > (uneccessarily) the number of relations. Of course, this also doesn't
> > solve the problem that all ternary and higher order relations (of which
> > there are a number in SUMO) will still be invisible in Protege or any
> > other frame system.
> >
> > This is a good example of why Protege is a bad choice for a formal
> > ontology expressed in logic.
> >
> > Adam
> >
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> >
> >
>
>--
>=============================================
>Patrick Cassidy
>
>MICRA, Inc. || (908) 561-3416
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>
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