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Re: Web Rule Language - WRL vs SWRL

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Wed, 29 Jun 2005 14:09:27 -0400
To: Ian Horrocks <horrocks@cs.man.ac.uk>
Cc: Bijan Parsia <bparsia@isr.umd.edu>, Jim Hendler <hendler@cs.umd.edu>, www-rdf-rules@w3.org, dreer@fh-furtwangen.de, Jos de Bruijn <jos.debruijn@deri.org>
Message-Id: <20050629180928.680E719E75F@kiferdesk.lmc.cs.sunysb.edu>


> On 28 Jun 2005, at 20:17, Michael Kifer wrote:
> 
> >
> > Ian,
> >
> > The difference is really between SWRL and everything else,
> 
> I don't understand what leads you to this bizarre conclusion! (See 
> comments bellow w.r.t. your N3 argument.)


I don't understand your argument either.


> > and SWRL should
> > be developed by a different WG, if there is a need for a rules language
> > sitting on top of OWL.
> 
> OK, so you favour option (c) - several working groups developing 
> unrelated rules languages. Interesting plan. Surely we should try to do 
> something better than that.


Do you have a better plan (and reasons to believe that it will succeed)?


> > N3 is essentially a different syntax for F-logic and its extensions 
> > (but
> > N3's semantics is defined by use cases ;-). As far as I can tell, with 
> > each
> > new presentation that I hear N3 is moving in the direction of LP.
> 
> I think that we should stick to discussing how things actually *are* 
> rather than directions in which you hope/believe they might be moving. 

I am discussing things as they already are. N3 now has a form of SNAF.

> Surely N3 is *actually* a different syntax for RDF, plus some rule-like 
> extensions. As we have already agreed, LP is semantically incompatible 
> with RDF, so it does not make sense to say that N3 can be included in 
> LP.


Did we agree about RDF?  I didn't notice that.


> And what about the various business rules people that presented at the 
> rules workshop? Are they also "moving in the direction of LP"? Didn't 
> look like it from where I was sitting!

There was a number of different presentations. Mostly usecases.
Most people didn't address the foundations at all.


	--michael  


> 
> Ian
> 
> 
> 
> >
> >
> > 	--michael
> >
> >
> > Ian Horrocks wrote:
> >>
> >> On 23 Jun 2005, at 05:54, Michael Kifer wrote:
> >>
> >>>
> >>>
> >>> Jim,
> >>> So, you are saying that LP is at the same stage as DAML+OIL before
> >>> standardization. What is needed is to work out the details --
> >>> typically a
> >>> job for a working group.  Who disagrees with that?
> >>
> >> I do not agree that the current situation w.r.t. "rules languages" is
> >> comparable to the one appertaining w.r.t. "ontology languages" when 
> >> the
> >> WebOnt working group was chartered. At that time there was a single
> >> candidate ontology language around which a broad consensus had already
> >> been built (e.g., through the merging of the OIL and DAML-Ont 
> >> efforts).
> >> Currently there are several competing rules language proposals, with 
> >> no
> >> obvious (to me) leading contender.
> >>
> >> I also disagree with the suggestion that a Working Group is likely to
> >> be able to resolve major technical problems - if you look at what went
> >> in to WebOnt (DAML+OIL) and what came out (OWL), you will see that 
> >> they
> >> are relatively similar. This is not to minimise the quality or 
> >> quantity
> >> of the work carried out within WebOnt - it simply illustrates how
> >> difficult it is to get a large and heterogeneous WG to agree on
> >> anything, never mind agreeing on significant technical changes, and 
> >> how
> >> much effort is required to go from a prototype to a finished product.
> >>
> >> So, your argument leads me to the conclusion that either (a) one of 
> >> the
> >> candidates should be (arbitrarily?) chosen for standardisation, (b) a
> >> WG should be established without any clear indication as to what 
> >> should
> >> be standardised, or (c) several WG's should be established - one for
> >> LP, one SWRL, one for N3, etc. Option (a) is hardly likely to promote
> >> consensus building, option (b) seems to be a recipe for years of
> >> unproductive argument, and option (c) would be very costly (for both
> >> the W3C and the semantic web community), and very confusing for those
> >> considering the adoption of semantic web technology.
> >>
> >> A fourth alternative, and one that I think several people in this
> >> thread have been arguing for, is to continue working (in whatever
> >> context) towards an architectural framework that provides for a better
> >> integration between First Order and LP based languages. We should then
> >> be able to achieve the broad consensus which is, I believe, a 
> >> necessary
> >> (or at least highly desirable) precursor to the initiation of a
> >> standardisation activity.
> >>
> >> Regards,
> >>
> >> Ian
> >>
> >>
> >>
> >>
> >>>
> >>> And you didn't need to defend OWL because nobody was attacking it.  
> >>> Our
> >>> discussion was about the 1-stack vs. multi-stack architectures. Since
> >>> in a
> >>> previous email you said that you are "not against a multi-stack
> >>> solution"
> >>> then I don't see what is the point of contention (at least at the 
> >>> high
> >>> level). I believe that everybody agrees that the more integration --
> >>> the
> >>> better. We just don't believe that integration of the leading useful
> >>> technologies to the point that only one stack is left is possible.
> >>>
> >>>
> >>> 	--michael
> >>>
> >>>
> >>>> 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
> >>>> began.
> >>>>   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...
> >>>>   JH
> >>>> 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]
> >>>>>>
> >>>>>> http://www.sciam.com/article.cfm?articleID=00048144-10D2-1C70
> >>>>>> -84A9809EC588EF21
> >>>>
> >>>> -- 
> >>>> 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 Wednesday, 29 June 2005 18:10:26 GMT

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