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Re: Rules WG -- draft charter -- Rules, vs. OWL alone, in Semantic Web Services

From: Benjamin Grosof <bgrosof@mit.edu>
Date: Fri, 14 Nov 2003 14:39:00 -0500
Message-Id: <>
To: Jack Berkowitz <jack.berkowitz@networkinference.com>, www-rdf-rules@w3.org, Sandro Hawke <sandro@w3.org>
Cc: phayes@ihmc.us, adrianw@snet.net, stabet@comcast.net, kifer@cs.stonybrook.edu (Michael Kifer)
Hi Jack and all,

At 07:10 PM 11/13/2003 +0000, Jack Berkowitz wrote:

>Just a couple of basic comments on the draft that has been circulated.
>The first is a critique.  The second I need some help understanding.
>You state in the draft:
>"Semantic Web Services work such as OWL-S [[[benj: [give OWL-S ref] and 
>the Semantic Web Services Initiative (SWSI) [give SWSI ref, esp. to the 
>draft requirements spec of its Language Commmittee] ]]] has found that 
>while OWL allows a lot to be stated, there is a clear need for rules for 
>this work. [[[benj: Rules in particular are critically needed for 
>representing several aspects of such service descriptions, e.g., 
>security/trust policies, proposed or committed contracts/deals, exception 
>handling, and semantic translation between composed sub-services. /* These 
>are identified in the SWSI requirements documents */ "
>I do not feel that this justification is accurate, in particular with 
>regards to the "e.g." elements.  We are today able to represent security 
>policies, proposed/committed contracts, and semantic translations using 
>OWL-DL and encoding this elements as axiomatic expressions in a very 
>direct fashion and without issue.  In turn, knowledge of these can be 
>obtained through querying our inference platform.  As stated, the 
>justifications do not stand up.

Perhaps I didn't state it clearly enough.  Here's another try.

There is a consensus in the OWL-S and SWSI efforts, as well as in DAML, 
that for many areas of Semantic Web Services OWL is NOT sufficient as a KR 
to meet their requirements.  This goes far beyond enactment.

Wrt things like security/trust policies, proposed or committed 
contracts/deals, exception handling, and semantic translation between 
composed sub-services, we can make an analogy.

A bear can stand on two legs.  It can even walk, after a fashion.  But it's 
not really cut out for it, and there's another kind of creature that can do 
it much better.  OWL is the bear, in these SWS areas.

Rules, together with OWL, can represent more (useful for SWS things 
expressively, and can represent often more naturally the (useful for SWS) 
things that OWL can represent alone.


>  However, if you were to amend your justification to areas that are 
> clearly in the domain of Logic Programs -- the ENACTMENT of policies or 
> alternate courses of action in reaction to problems, then I believe your 
> statement will be more robust.
>furthermore in the draft, you explicitly call out elements regarding query 
>and operators, with the following:
>"A standard library of built-in terms such as integer sum, string 
>concatenation, and the like, based on the XML Query functions and 
>operators is in scope, since it clearly contributes to interoperability 
>and utility of rules technology. These functions shall be implemented as 
>RDF properties (using RDF Lists to handle n-ary functions, as implemented 
>in cwm). While it is not required that the URIs of the RDF properties be 
>the same as those of the XQuery functions and operators, where RDF 
>functions and operators terms correspond to XQuery ones, the semantics 
>should be exactly equivalent. @@justify - conversion, reuse of code etc."
>In my opinion, partly this is the wrong approach, but I freely admit that 
>I am missing something, so read my understandings and then correct me, please:
>The W3C has just managed to get XQuery energized, yet we are looking to 
>redo that work in yet another recommendation or method?  Why?  Rather than 
>specify that a re-implementation of the semantics of XQuery be done, why 
>not study the requirements of Xquery that capture the additional semantics 
>and uses needed for OWL & OWL-RULES and make a cogent argument to the 
>XQuery working group to formally extend their recommendation to encompass 
>additional capabilities?  If someone needs exact semantics, why can't they 
>just us XQuery as is??  We have hybrid reasoning working here with a Logic 
>Program that calls out to an XQuery to hit a compiled OWL knowledge base, 
>and it works fine.
>People are going to be spending the next two years building applications 
>using XQuery to hit XML sources as they transition off of straight 
>SQL.  In the next two years, you are hopefully going to see several 
>million people with some ability to use XQuery.  Therefore, companies 
>today are moving in that direction (like us).  If there is yet another 
>query method, at a minimum, this will force me to change software and 
>retrain integrators all over again.  The cost impact will be prohibitive.
>The W3C membership is already asking integrators and developers to learn 
>XQuery.  Saying to them that they need to learn and implement yet another 
>query-oriented or operation-oriented methodology in order to get to the 
>semantic web seems to be yet another barrier in an already bumpy road.  We 
>should be striving for less recommendations, but ones that hang together.
>Best regards,
>Jack Berkowitz
>Vice President, Engineering
>Network Inference (Holdings) Ltd
>+44 (0)20 7616 0700

Prof. Benjamin Grosof
Web Technologies for E-Commerce, Business Policies, E-Contracting, Rules, 
XML, Agents, Semantic Web Services
MIT Sloan School of Management, Information Technology group
http://ebusiness.mit.edu/bgrosof or http://www.mit.edu/~bgrosof
Received on Friday, 14 November 2003 14:37:15 UTC

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