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

From: Dieter Fensel <dieter.fensel@deri.org>
Date: Wed, 24 Aug 2005 20:12:22 +0200
Message-Id: <5.2.0.9.0.20050824194910.00c38cf8@mail1.uibk.ac.at>
To: public-rule-workshop-discuss@w3.org
Cc: Christian de Sainte Marie <csma@ilog.fr>

From

: Christian de Sainte Marie 
<<mailto:csma@ilog.fr?Subject=Re:%20A%20Rule%20Interchange%20Format%20VS%20a%20Rule%20Language%20for%20Interoperability%20%20and%20other%20issues&In-Reply-To=%3C430C61A0.9070602@ilog.fr%3E&References=%3C430C61A0.9070602@ilog.fr%3E>csma@ilog.fr> 

Date

: Wed, 24 Aug 2005 14:01:36 +0200
Message-ID

: <430C61A0.9070602@ilog.fr>
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: 
<mailto:public-rule-workshop-discuss@w3.org?Subject=Re:%20A%20Rule%20Interchange%20Format%20VS%20a%20Rule%20Language%20for%20Interoperability%20%20and%20other%20issues&In-Reply-To=%3C430C61A0.9070602@ilog.fr%3E&References=%3C430C61A0.9070602@ilog.fr%3E>public-rule-workshop-discuss@w3.org 




 >(Sorry for the long posting, and the, at least partially, obvious
 >content: I am trying to clarify my understanding as much as to advance
 >the discussion. I hope this helps)

Dear Christian,

It is always refreshing to get valid requirements from industry on what is
needed, but not always similar insightfully to listen to how it can be 
achieved.
Christian, with all respect you seriously contradict yourself on two 
essential points:

1) You want to have an exchange language that cover 100% of all rule languages
(even you admit later that you expect only 80% of the things actually exchanged
between different rule languages). However, FOL CANNOT even express most basic
things of rule languages. It is well known from literature that even the most
simple deductive language can be used to derive the deductive closure of a
relation based on its minimal model semantics. This is also implicitly the
point made in [1]. FOL with its multi-model semantics CANNOT express the
deductive closure of a relation. For this you would need second-order logic.
That is, given your own criteria of covering most if not all of existing rule
languages your proposal using FOL fails already for one of the *** most 
simplest
*** rule languages!

2) Your proposal to soundly translate between different rule languages by
mapping in and out of FOL brakes since most/all (?) rule languages use a 
different
semantics than FOL. That is, given your own requirement your proposal using FOL
fails!

Therefore, your requirements could only be fulfilled in the way you propose
either by second-order logic or by using FOL only as an exchange syntax 
without
attached semantics BUT NOT BY FOL WITH MULTI-MODEL SEMANTICS as it is defined
in any text book. In conclusion; I only see three ways to go (truly spoken only
one actual pathway to go):

         - Using second-order logic (I wait for the genius that is going to 
propose this)
         - Using only an exchange syntax which brings us close to the usage 
of XML
         - Asking ourselves whether there is a way out of this dilemma. And 
in fact,
         there is!

Why not going the other way around? Identifying the 80% that vendors and 
users thinks
they need (and are therefore subject for broader exchange), put them in a 
simple
language and define a unique model semantics for it as it is used by most 
systems
anyway (in case they use a model theoretical semantics at all)?


         -- dieter

[1] Ian Horrocks, Bijan Parsia, Peter Patel-Schneider, and James Hendler: 
Semantic web architecture: Stack or two towers? In Third Workshop on
Principles and Practice of Semantic Web Reasoning, Dagstuhl, Germany, 
September 2005.

----------------------------------------------------------------
Dieter Fensel, http://www.deri.org/
Tel.: +43-512-5076485/8
Received on Wednesday, 24 August 2005 18:17:03 GMT

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