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RE: [OWLWG-COMMENT] Punning and the "properties for classes" use case

From: Michael Schneider <schneid@fzi.de>
Date: Fri, 2 Nov 2007 20:23:14 +0100
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A04A8DE5@judith.fzi.de>
To: "Evren Sirin" <evren@clarkparsia.com>
Cc: <public-owl-dev@w3.org>, <jjc@hpl.hp.com>, <alanruttenberg@gmail.com>

Hi, Evren!

Evren Sirin wrote on November 02, 2007:

>You are correct in your understanding of punning. It is true that 
>punning semantics is strictly weaker than OWL-Full semantics and the 
>inferences you will get will be a subset of OWL Full entailments. But 
>what is the alternative? Without punning, any ontology where 
>classes are 
>used as instances will not be allowed in OWL-DL and rejected by OWL-DL 
>reasoners. So you have to use an OWL-Full reasoner which means you are 
>stuck with incompleteness (I'm not aware of any OWL-Full reasoner) and 
>depending on which OWL-Full reasoner you use incompleteness come from 
>different parts (e.g. some reasoners doesn't support 
>others don't support owl:oneOf, etc.). At least with punning you know 
>what causes the incompleteness. 

If metamodelling brings us away from decidability (this is the real problem,
right?), then I see two alternatives:

  (1) Stop hunting for metamodelling capabilities in OWL-1.1-DL.
      Metamodelling, even in a restricted form, would really be 
      a useful feature, but the community has already learnt 
      to live with the current situation.

  (2) Add general metamodelling (not necessarily complete OWL-Full support)
      to OWL-1.1-DL, and remove the requirement for decidability.
My personal preference would be to go the (1)-way for OWL-1.1-DL, as a fast,
save and conservative solution. And then (later) start thinking about an
additional language somewhere in the middle between OWL-1.1-DL and
OWL-1.1-Full, which I would call "OWL-UseFull". ;-) This language would have
a few additional most-wanted features (like metamodelling), but it does not
allow you to build any of those scary (and useless) constructs, which you
can actually build in OWL-Full.

A caveat would be that decidability could then not be a requirement anymore.
But I would not stop thinking about this proposal from the start on. One
would have to determine if this brings real problems in /practice/. In fact,
there is a lot of useful software around for undecidable problems, without
getting into practical problems, as long as this software is used in a
meaningful way (parser generators, type checkers for the Haskell language,
automatic reasoners for FOL and HOL, computer algebra systems).
>I might be wrong but I'm not aware of 
>anything other than sameAs-equivalentClass (and possibly 
>equivalentProperty) relation that would cause the punning semantics 
>incomplete w.r.t OWL-Full semantics.

I think this alone already suffices, no need to look for more. :)

>I'd be interested in seeing if 
>there is any other use case where punning semantics does not entail 
>everything OWL-Full semantics does.
>FWIW, punning has been implemented in Pellet for years and I don't 
>remember any of our users calling it "confusing" or "useless".

That's interesting to hear, I did not know this. But has this also been a
feature in Pellet which has been /applied/ by /many/ users for years? 
>I believe 
>it is more of a personal style choice to use punning (it might be 
>confusing for some people but not others). I think it is a 
>viable option 
>for "properties for classes" use case (though I'd personally call it 
>classes as instances use case)

Yes, better. And in fact, the property discussion in my mail was a little
bit redundant. Though my intended message was in effect that with punning it
is easy to believe that one can assign a property to a class, while one
actually assigns it to some equally named, but possibly completely different
individual resource. Now, after Alan's answer, I am not certain anymore, if
it is still possible that an individual can be different from an
equally-named class. This is a core question to me.

>because most of these use cases do not 
>depend on sameAs-equivalentClass relation.

I think that this relation is so fundamental, that you cannot really avoid
to stumble over it ever and ever again. Perhaps, I will come up with other
examples in the future, which demonstrate the /practical/ problems (but not
before my headache produced by this topic has gone away again ;-)).



Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
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Email: Michael.Schneider@fzi.de
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Received on Friday, 2 November 2007 19:23:36 UTC

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