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Re: NAF v. SNAF - where is this being addressed?

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 29 Jun 2005 14:08:30 -0400
Message-Id: <p0620071cbee890d6d568@[]>
To: Michael Kifer <kifer@cs.sunysb.edu>
Cc: public-rule-workshop-discuss@w3.org
Mike - I didn't say that SNAF was controversial.  But it also cannot 
be theoretical in the output of a Working Group (the context of my 
email) -- an eventual charter has to include specific wording that 
addresses this goal -- let me explain using examples from the Web 
Ontology Group Charter that eventually led to OWL -- this charter is 
in http://www.w3.org/2002/11/swv2/charters/WebOntologyCharter

i. If there is a generally agree upon approach with a well-understood 
semantics and a web-realizable syntax, then the charter should 
specify this as a starting place
      (for example, the Web Ont Charter stated that we must start from 
ii.  If there isn't, then the specific goals of the mechanism to be 
developed has to be stated (for example, the Web Ont charter 
specified with respect to semantics that it must "clearly delineate 
what is, and is not, entailed from any particular language construct 
or combination thereof")

So, in thinking about creating a working group, I am a bit confused 
as to where we stand with this -- I know it is possible to do 
something SNAF related, but now we must take it to the next level.
p.s. Mike, let me use an example that might help you -- in the paper 
you and Subrahmanian did, you proved all sorts of great things about 
annotated logics.  However, if we were goign to do a standardization 
of a particular annotated logic, we would have to be much more 
specific and define a particular annotation set and corresponding 
logic.  Your paper proves this could be done, and that it should be 
done, but doesn't outline the specifics, so a charter would need to 
limit the design space to the maximum degree (which is the goal of a 
WG charter, and what makes them so danged hard to write)

At 12:20 -0400 6/29/05, Michael Kifer wrote:
>>  All, forgive me if I missed something since I wasn't able to attend
>>  the workshop.  My understanding from the workshop report, and from
>>  discussion with Tim BL and others afterwards, was that NAF wasn't
>>  going to make sense, but SNAF would -- that is, on the Web, if there
>>  is not a mechanism for defining the "KB" (graph) that a set of rules
>>  is applied to, there's not way to use a geenralized negation as
>>  failure -- i.e. I cannot say to the "whole web" that someone can be
>>  assumed to have two children unless it is shown they have a different
>>  number.  Instead, I need a way to designate the dataset that a rule
>>  like this is applied to.  SNAF, as I understand it, was the term
>>  being used to designate this.
>Yes, SNAF is a generalization of NAF, and many people (including me) mean SNAF
>(some prefer to call it scoped default negation) when they say NAF.
>>    Yet, reading just about all the mail since the workshop, I haven't
>>  seen this referred to at all (and it's not really discussed in the
>>  WRL vs. SWRL or other threads currently being discussed in rdf-rules
>>  and sws-ig)
>Some systems, like FLORA-2, inherently support SNAF. WRL was supposed to
>have SNAF, but not in 1.0. This is work in progress. SWSL-Rules will also
>have SNAF, but not in 1.0. (These two languages are actually quite close to
>each other.)
>>    Seems to me if I see your rule set includes a NAF-based rule, and
>>  you give me a conclusion to something, that if I don't know what
>>  graph/KB/DB that was applied to, then I have no way to know whether I
>>  can use your result in my application
>Note that SNAF applies not only to data sets, but also to rulesets.
>>     Seems to me also that this has a big effect on the charter, as I
>>  don't know if there is an agreed upon use of SNAF for the Web, and
>>  would need to be something the WG would be required to elucidate.
>SNAF is non-controversial, I think. It is a simple extension of NAF.
>	--michael 
>>    -JH
>>  p.s. Note that in datalog, there is always the assumption that the
>>  rules and a particular database can be linked - on the Web, that is
>>  not necessarily true.
>>  --
>>  Professor James Hendler			  Director
>>  Joint Institute for Knowledge Discovery		  301-405-2696
>>  UMIACS, Univ of Maryland			  301-314-9734 (Fax)
>>  College Park, MD 20742 

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 18:10:16 UTC

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