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Re: A Rule Interchange Format VS a Rule Language for Interoperability and other issues

From: Christian de Sainte Marie <csma@ilog.fr>
Date: Wed, 24 Aug 2005 17:43:15 +0200
Message-ID: <430C9593.1020107@ilog.fr>
To: Gerd Wagner <wagnerg@tu-cottbus.de>
CC: public-rule-workshop-discuss@w3.org

Hi Gerd,

Gerd Wagner wrote:
>>If FOL is not a good 
>>candidate (as Jim at least hinted), I would be interested to 
>>understand 
>>why; and we would also need to find out what would be a good 
>>candidate;
> 
> 
> What do you mean by FOL? Do you mean classical standard
> (i.e. textbook) first-order predicate logic? Or do you
> mean Common Logic, which is also a FOL (since its 
> higher-order constructs can be eliminated)? Or do you
> mean partial first-order predicate logic, which would
> be more suitable, since it allows indeterminate truth
> values, as we have them in SQL and OCL?

I had classic/textbook first-order predicate logic in mind. But, as I 
said, any formalism with a sufficient expressiveness and a well-know 
semantics would do ('sufficient expressiveness' meaning: most practical 
rule languages can map onto it easily and completely enough, where 
'most' and 'easily and completely enough' remain to be defined; and a 
'well-known semantics' meaning one that the developers of software to 
translate rules between the RIF and a specific language do not need a 
PhD in logics to know and understand it).

As regards indeterminate truth values, I do not know: could you give me 
an example where you need indeterminate truth values to express a rule?

>>- Non-monotony: most applications/engines/rule bases that 
>>rely on SNAF 
>>also rely on monotonic inference/languages (well, I do not know for 
>>most; but some certainly do). It works because they actually rely on 
>>bounded monotony, only the bound is implicit (and, in most of 
>>the cases, obvious: a session, an inference cycle, whatever). 
> 
> How would you define your notion of "bounded monotony"? 
> It's not clear for me what you mean by that.

Oh, I have only a naive notion, here; nothing that amounts to a definition.

What I had in mind is what happens, for instance, in an application 
where the rules operate on the data in a data base: typically, the 
system will operate under the closed-world assumption, it will rely on 
negation as failure within the scope of the DB, and it will infer 
monotically, until there is a change in the database (change that can be 
induced by the application of a rule, as in a production system, or that 
can result from purely external events): in that case, the reasoning 
just restarts with the new state of the DB. The inference is monotonic 
(no defeasible inference), but bound by the next change in the DB.

Does it make sense?

Christian
Received on Thursday, 25 August 2005 11:00:45 GMT

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