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Re: Web Rule Language - WRL vs SWRL

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 22 Jun 2005 23:07:46 -0400
Message-Id: <p06200792bedfd44fc583@[]>
To: Michael Kifer <kifer@cs.sunysb.edu>
Cc: Bijan Parsia <bparsia@isr.umd.edu>, www-rdf-rules@w3.org, dreer@fh-furtwangen.de, Jos de Bruijn <jos.debruijn@deri.org>

Mike - I think you're missing the point of the "webbie" nature of OWL 
and the difference from traditional KR, but I have written that up 
too many times to do it again here.  With LP, the question is how I 
can use your rules/program/etc. in part to get a "network effect" and 
to make it so I can link together the logics and logic programs as 
easily as I link web pages.  It;s not that no one has good research 
ideas on how to do that, it's how to bring those to fruition and 
greater use that is the key
    The ontology stuff in OWL, which is not actually DL (even  OWL DL 
departs from traditional DL in some interesting ways, but OWL Full is 
the one I care most about) is based on many years of work in AI, and 
was explored on the web long before OWL was done - cf the SHOE work 
my group did (still a high hit at Google - so just google "shoe") and 
that was followed by XOL, OIL, and others before the standardization 
  I think the LP stuff is in similar state - a basic idea has been 
fleshed out, some variants are being explored, and there is a govt 
interest in pushing for a de facto standard.   But  going from there 
to the finish line is where a lot of the time and blood goes in -- 
it's in making the stuff fit with what else is out there in the Web. 
We had to do a lot of work to make OWL fit in with RDF and other 
languages it needed to interoperate with, and a web rules language 
needs to be defined with the other things already in the space it 
wants to play in (thus the "stacks" issue - if it wants to be in a 
Sem Web stack, it needs to play with other SW stuff; if it wants to 
be in the XML stack, it needs to play nice with XML stuff like Xquery 
and Xpath, etc.
  And that is the discussion we are having -- but if we can nail this 
stuff, the result is worth it -- OWL is certainly the most used 
KR/ontology langauge in the history of AI as best anyone can tell, 
and if we want the Web Rules Language to flourish we want it to grow 
like the Web does, not like rules languages have -- nothing wrong 
with the latter, but there's a whole lot more Web pages out there 
than logic programs, and it's a lot more fun to play in the 
exponential growth space :-)
  anyway, we're all working for same ends, just different means, and 
finding the consensus space in the middle is wondefully non-fun, but 
worth it in the end

  Ok, end of crap, back to technical issues and Greek symbols...
p.s. please note - I spent many years of my career arguing against DL 
and doing scruffy AI - yet here I am defending OWL - why?  because 
the design time and fights over the details of a number of use cases 
ended up creating something pretty damn useful -- both in the OWL DL 
space and in the OWL Full space -- so somehow the process worked...

At 20:41 -0400 6/22/05, Michael Kifer wrote:
>Jim Hendler wrote:
>>  Mike - I think you misunderstand the stuff about stacks and etc -- I
>>  hope my use cases (in public-sws-ig@w3.org for those just joining the
>>  conversation) would help make it clear that these are not separate
>>  and unrelated stacks, nor are they identical things -- the key is
>>  figuring out how the stacking works and how things interact -- I'm
>>  not against a "multi-stack: solution, but as far as I am concerned
>>  the more overlap the better, and I am fairly sure that we can do
>>  significantly better than DLP in terms of providing a useful web
>>  rules language that interacts well with the existing, and becoming
>>  more widely used, ontology spec.*
>I think it is not just me, but a number of people who read your paper on
>the two stacks may have misunderstood it. At least one way to understand
>what is said there is that 1 stack is good and 2 is not.
>If there is another way to understand it (as advocating a multi-stack
>architecture) then this second meaning is deeper than I was able to dig up.
>>    Seems to me the key is exploring how to get maximum interoperability
>>  between the important work in BOTH areas (and I defy you to go back
>>  through this discussion and find any email where I haven't said I'm
>>  in favor of a web rules language)
>You didn't say this and I didn't say that you said this.  I was
>focusing on what I think were technically inaccurate claims in your email
>regarding the layering of WRL on top of DLP (where WRL is taken to mean the
>particular language under this name and not "a" generic web rules language).
>>  and also how to get the Web rules
>>  to join in the growing whole that is the semantic web -- it's not the
>>  same as applying LP in the Web area -- I argued for nearly a decade
>>  about the difference between Web Ontology and standard AI KR
>>  languages, and OWL has some significant differences from traditional
>>  AI (see the OWL FAQ [1] and the discussion of KR  back in the 2001
>>  Scientific American article [2])
>Not "applying LP in the Web area" but "adapting LP to the Web".
>Technically, OWL is an adaptation of DL to the Web with some additional
>research needed to accommodate RDFS.  But in the LP area this research has
>already been done years ago.
>>  This latter, btw, explains why URIs
>>  are not just some wildassed thing, they're crucial to the Semantic
>>  Web in a very deep way - read the Sci Am or any of Tim's discussions
>>  of this issue.
>Of course URIs are crucial. After all, they are object identifiers, so they
>are as crucial as any notion of an Id.
>But do they imply/require a new kind of KR?  There are interesting new
>problems that stem from the architecture, but don't make it sound as if the
>"old KR" is out of the window and adapting it to the new architecture is a
>hard or pointless exercise. The LP paradigm is as applicable to the Web as
>DL, if not more. (I, of course, think that it is more :-)
>>    so, I don't see this as in any way being a discussion of rules vs.
>>  ontology -- in fact, I cannot think of any dumber way to approach it
>>  -- rather it seems to me we're trying to explore where these things
>>  can overlap to the benefit of users and of the Web -- that strikes me
>>  as a very worthwhile pursuit
>The term "rules" is ambiguous in the context of our discussion. If you said
>"I don't see this as in any way being a discussion of *LP* vs. ontology"
>then this is exactly what I was trying to say. As I remarked above,
>the 2tower paper **appears** to be arguing that LP+OWL in a 2-stack
>architecture is a nonstarter.
>	--michael
>>    -JH
>>  [1] http://www.w3.org/2003/08/owlfaq.html
>>  [2]

Professor James Hendler			  Director
Joint Institute for Knowledge Discovery	  	  301-405-2696
UMIACS, Univ of Maryland			  301-314-9734 (Fax)
College Park, MD 20742	 		  http://www.cs.umd.edu/users/hendler
Received on Thursday, 23 June 2005 03:08:26 UTC

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