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Re: To embed or combine

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Mon, 10 Sep 2007 12:45:50 -0400
To: Jos de Bruijn <debruijn@inf.unibz.it>
Cc: Chris Welty <cawelty@gmail.com>, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
Message-ID: <17377.1189442750@cs.sunysb.edu>


> Michael Kifer wrote:
> >>> The most important argument is that the embedding stands on its own feet,
> >>> while the combined semantics is of limited use, since we need the embedding
> >>> anyway.
> >> We don't necessarily /need/ the embedding if we define a model-theoretic
> >> combination [*], it is just nice to have as an appendix, to show how
> >> reasoning can be done with the combination.  Just like, as you suggested
> >> in an earlier e-mail, we could use the model-theoretic combination in an
> >> appendix as a justification for choosing a particular embedding in case
> >> we go for the embedding.
> > 
> > Publish the semantics without the embedding, and see what the reaction will be.
> > I suspect that it will be: Huh? What do I do with this?
> 
> Yes, probably.  And publish the embedding without any justification and
> the reaction will be:  Why this embedding?
> 
> > 
> > The point is that the embedding is trivial and easy to explain. 
> 
> It is certainly not trivial.
> Whether it is easier to explain is a matter of point of view, and also
> depends on to whom you are explaining it.

The embedding is trivial:

(s p o) ---> s[p->o]

all the rest are just commentaries. This is why I feel that the semantics
is not necessary.


	--michael  


> >>> Regarding (2) my argument was not what you wrote, but that Jos' document
> >>> essentially specifies a full-blown combined language. The embedding alone
> >>> is sufficient in my view. It allows people to use rules and RDF together,
> >>> but it does not define a normative combined language.  By defining an
> >>> embedding, we already achieve all the goals with respect to RDF, which were
> >>> listed in the charter.
> >> Whether we define the semantics of the combination based on a model
> >> theory or based on an embedding in RIF, in both cases we define a
> >> combined language, which is normative.
> > 
> > You can put it this way, but then any embedding of any rule language into
> > RIF can be viewed as a combined RIF-LanguageX language. Normally people
> > will not view it this way.
> 
> The point is that RDF is not a rule language, but a data language. So,
> people will want to exchange rules referring to RDF data sets.  The
> agents receiving the rules and the data will have to *combine* them in
> some way in order to process them.
> 
> When exchanging any rule language using RIF, nothing will have to be
> combined, so in this case (as you said) people will indeed not view it
> as a combined language.
> 
> 
> Best, Jos
> 
> 
> > 
> > 
> > 
> > 	--michael  
> > 
> > 
> >> Best, Jos
> >>
> >>>
> >>> 	--michael  
> >>>
> >>>> <chair>
> >>>> The status of the discussion regarding Jos' RDF compatibility section appears to 
> >>>> be mired in whether the normative semantics of RDF in RIF should be specified in 
> >>>> the model theory through a "combination" of RIF and RDF semantics, or through an 
> >>>> "embedding" of RDF semantics in RIF (as rules).  The two approaches have been 
> >>>> shown by Jos to be equivalent.
> >>>>
> >>>> At the moment I have not seen any technical arguments supporting one approach or 
> >>>> the other.  Michael prefers the "embedding" on the basis that:
> >>>>
> >>>> (1) the "combination" is more complicated than the "embedding" and thus more 
> >>>> difficult to understand.
> >>>>
> >>>> (2) it is not our job viz. our charter to specify a model theoretic approach to 
> >>>> the RDF/RIF combination
> >>>>
> >>>> Jos seems to prefer the "combination" and argues re: (1) that:
> >>>>
> >>>> (3) it is no more difficult to understand the "combination" than the RIF model 
> >>>> theory.
> >>>>
> >>>> As chair, my own read of the charter does not provide any particular help on 
> >>>> (2), I'm not quite sure what Michael is referring to there.  It is certainly our 
> >>>> job to specify how RIF and RDF should be used together, and as chair I interpret 
> >>>> this as meaning we should have a normative standard for that.
> >>>>
> >>>> Thus, as suggested by Michael, it seems to me we are at a difference in 
> >>>> preference only, and I see no alternative other than to call a vote.  It seems 
> >>>> to me the vote is about which approaches to make *normative*:
> >>>>
> >>>> 1) The model-theoretic "combination" of RIF and RDF is normative
> >>>> 2) The "embedding" of RDF semantics as RIF rules is normative
> >>>> 3) Both the "combination" and "embedding" are normative (What would that mean?)
> >>>> </chair>
> >>>>
> >>>> -Chris
> >>>>
> >>>>
> >>>> -- 
> >>>> Dr. Christopher A. Welty                    IBM Watson Research Center
> >>>> +1.914.784.7055                             19 Skyline Dr.
> >>>> cawelty@gmail.com                           Hawthorne, NY 10532
> >>>> http://www.research.ibm.com/people/w/welty
> > 
> 
> -- 
> Jos de Bruijn            debruijn@inf.unibz.it
> +390471016224         http://www.debruijn.net/
> ----------------------------------------------
> The third-rate mind is only happy when it is
> thinking with the majority. The second-rate
> mind is only happy when it is thinking with
> the minority. The first-rate mind is only
> happy when it is thinking.
>   - AA Milne
Received on Monday, 10 September 2007 16:46:24 UTC

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