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Re: [UCR] RIF needs different reasoning methods

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Mon, 13 Mar 2006 05:02:11 -0500
Message-Id: <f25677b037b036b6bb99bcd0da014a29@isr.umd.edu>
Cc: <public-rif-wg@w3.org>, "'Sandro Hawke'" <sandro@w3.org>
To: "Gerd Wagner" <wagnerg@tu-cottbus.de>

On Mar 13, 2006, at 4:33 AM, Gerd Wagner wrote:

>> My understanding is that derivation rules and integrity
>> constraints are
>> just a bifurcation of Horn rules (or sometimes the two halves of
>> something beyond Horn).  As such they fit easily into the same
>> semantics.
>
> Not really, there are both syntactic and semantic
> differences:
>
> - derivation rules, in general, correspond to Gentzen
>   sequents;
[snip]
> - integrity constraints, in general, correspond to
>   sentences of some logic (which may be classical FOL,
>   temporal FOL or some modal FOL); as emphasized by
>   SBVR,
[snip]
> Given all these differences, how can you say "they
> fit easily into the same semantics"?

While I wouldn't have said it the way Sandro did, there are attempts to 
formalize integrity constraints (with all their semantics and 
pragmatics) using the K and A operators (i.e., in MKNF):
	http://citeseer.ist.psu.edu/237686.html
	http://www.cs.utexas.edu/users/vl/mypapers/mbnf.ps

(Of course, using K & A is a little like using continuations to model 
threads and exceptions....you can do it, and it's cool, but, uh, it's 
generally harder than direct approaches.)

> The fact that, in certain circumstances, they may both
> take the form of a Horn formula does not mean they
> have the same semantics
[snip]

That I *heartily* agree with.

Cheers,
Bijan.
Received on Monday, 13 March 2006 10:02:23 GMT

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