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Re: Reflexivity and antisymmetry uses cases?

From: Dave Reynolds <der@hplb.hpl.hp.com>
Date: Wed, 17 Jan 2007 12:02:54 +0000
Message-ID: <45AE106E.7050105@hplb.hpl.hp.com>
To: Gerd Wagner <wagnerg@tu-cottbus.de>
CC: public-owl-dev@w3.org

Gerd Wagner wrote:
>> 3) A certain skirting around the issue of how RDF and OWL semantics  
>> differ from the usual database view of the world. Domain and Range  
>> are a constant source of confusion. Open world assumptions also  
>> makes, e.g. cardinality restrictions, not behave the way one would  
>> expect them to. I think the choice of open world assumption is well  
>> motivated, 
> Is it really (in all cases)?
> I don't think that there was ever any deliberate design decision
> in favor of the "open world assumption" (OWA) versus the CWA in
> the making of OWL. The OWA is just in the baggage of classical 
> mathematical logic, so if you stick to that formalism, you get 
> it for free (without having any chance to reject or weaken it).

In RDF OWA was a deliberate design decision based on the intended use 
case of representing distributed web information. On the web you expect 
to often have partial information from one source and never know what 
other assertions might be "out there" that you haven't yet taken into 
account but might do so in the future.

Indeed the ability to have both partial models and to have models which 
have extra unexpected assertions have been key benefits for us in 
several of our applications.

That said the ability to perform closed world checking at certain points 
in an application can also be useful which is why we also support tools 
that help with this.

>> but we do need some ability to do closed-world reasoning  
>> such as constraint checking, and from a messaging point of view a  
>> more head-on approach to discussing  how and why both OWL and RDF  
>> differ from databases.
> Database languages, such as SQL, are based on computational
> experience and best practices. Their formalizations in
> computational logics do not imply the OWA. In fact, they
> seem to suggest a controlled co-existence of both the CWA
> and the OWA.
> In order to help RDF and OWL to be more compatible with
> computational best practices (such as the distinction
> between facts, rules and constraints), it may be necessary
> to abandon/relax its strict classcial logic semantics.

Maybe but be careful not to throw the baby out with the bathwater.

Received on Wednesday, 17 January 2007 12:03:25 UTC

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