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Re: Comments on * DRAFT * Rules Working Group Charter $Revision: 1.60 $

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Thu, 25 Aug 2005 11:38:26 -0400
To: Christian de Sainte Marie <csma@ilog.fr>
Cc: public-rule-workshop-discuss@w3.org
Message-Id: <20050825153826.A7762CB5D3@kiferserv.kiferhome.com>


Christian de Sainte Marie <csma@ilog.fr> wrote:
> 
> Michael Kifer wrote:
> > 
> > RuleML people have realized that there can't be a single super-language
> > into which everything can be translated with the same semantics. So, their
> > approach is that the semantics rests with the rules languages and RuleML
> > defines their XML serializations.
> > 
> > The dream of being able to take any rule-based language, map it into a
> > "superlanguage", push through the wire, and then map it to a different
> > rules language at the other end of the wire (with an equivalent semantics)
> > is a pipe dream - unachievable.
> 
> Fair enough.
> 
> But who would want to do that, anyway (mapping any rule from any one 
> language to any other one, be it through a single pivot language or 
> elsewise)? People write and/or use rules for a purpose and they will 
> want to share/retrieve rules for a purpose, too.
> 
> So, for all practical purposes, we are talking about a "superlanguage" 
> such that rules written in any language can be map into it, and then 
> mapped back into any other language, with an equivalent semantics, 
> provided that there exist a semantics-preserving mapping for that rule 
> between the initial and end languages. Or a "superlanguage" that would 
> work like that for a reasonable subset of the rules that can be written 
> in a reasonable subset of the rule languages (where reasonable must be 
> large enough for the superlanguage to add sufficient value to be worth 
> its development).

Christian,

Unfortunately, once you throw in negation, then the superlanguage dream
breaks into pieces. I am afraid that this grand superlanguage boils down to
just pure Horn rules. This is a very limited language in which you can't do
much at all. It is not worth the effort.

> My understanding is that this is what the charter describes.

The charter has several technical errors, which point into wrong (doomed)
direction.


> > At least, not through FOL. So, RuleML takes
> > a more pragmatic approach
> 
> Yes, RuleML is indeed a possibility, afaIu.
> 
> My concern with RuleML is that it seems to take a prescriptive 
> (top-down) approach to which languages can map into each other, whereas 
> my natural tendency would be to leave it to the users (I mean, e.g. 
> rules or application developers) to decide.
> 
> The bottom-up approach requires that the standard specifies graceful 
> failure behaviours, but it seems to me that it is more robust against 
> unforeseen usages (in that it allows them, which is what we want it to 
> be). And profiles can help, anyway (profiles differ from the RuleML 
> typology in that a user community can define -and publish- any profile 
> it finds useful).
> 
> Again, maybe I am dead wrong, but, then, I really need somebody to 
> explain why...

I understand your bottom-up approach, and this would be great -- no
question.  But it is theoretically unachievable. (It is sometimes useful to
know these things :-) RuleML people knew these things and tried to come up
with an approach that works and achieves what you want *partially*.  I am
not saying that RuleML necessarily "got it right," but if I were to start
looking for interoperability among rules I would have started by looking at
RuleML than at a document (draft charter) that has fundamental technical
flaws.


	--michael  
Received on Thursday, 25 August 2005 15:38:33 GMT

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