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Re: a simple question

From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Fri, 19 Dec 2003 21:08:10 -0500 (EST)
Message-Id: <200312200208.hBK28Aw07559@pantheon-po02.its.yale.edu>
To: www-rdf-rules@w3.org

   [Pat Hayes]
   I think we are talking at cross purposes and in fact agree on almost 
   everything except rhetoric.

Probably.  I certainly agree on much of what you say in your posting.
However, ....


What follows are several quotes from Pat's posting to the effect that
we can and should distinguish "techniques" from "justifications":

   This confuses two issues: strategies for useful reasoning are one 
   thing, justifications of conclusions are another. 
   There is a deep-seated fallacy surfacing here, to the effect that the 
   use of logic (or indeed anything else, but it seems to be usually 
   invoked by the use of the L-word) as a representational language 
   *requires* that a certain kind of mechanism be used to process it. If 
   No,  it has got nothing to do with showing anything about techniques. 
   People should, and will, use whatever techniques they find useful, 
   and good luck to them.  None of the SW specs (RDF, RDFS, OWL) say 
   anything about what  techniques can or must be used to process these 
   languages (except for owl:imports). 
   The burden is to show how conclusions generated in this way can be 
   published without misleading someone  who is unaware of the context 
   in which they were derived, and to provide for ways of publishing the 
   rules themselves so that their assumed preconditions of use can be 
   made clear.  Several ways have been suggested, including having a 
   distinct 'failure-negation' . My own favorite is to have a notation 
   for saying explicitly that some ontology is a closed world as far as 
   a namespace is concerned, and then NAF is just plain valid when 
   applied properly,and NAF and logicism can coexist on the Web happily. 
   We need both, but 
   we need to keep their roles clearly distinguished. To point out that 
   NAF is not a good foundation for truth-justification in general is 
   not to say that all SW reasoning must be done by clunky 
   general-purpose inference engines.

It's this distinction between techniques and justifications that I
want to deny.  I wish it were not so.   

Here's how I would rephrase your position: For every computation that
leads to a conclusion, it is possible to factor it into a set of
assumptions plus a proof (within some commonly accepted system) that
the conclusion follows from the proof.  I predict that in most cases
too much information will be hidden in the assumptions; and that no
one will really know how to check them.  This is meant to be an
empirical prediction.  I may turn out to be wrong, but my past
experience makes me doubt it.

In the following fragment, I believe you overstated your case:

   In fact a reasoner is not even obligated to use a valid or guaranteed
   correct inference method. It might for example cut corners by assuming
   names are unique. its conclusions will not be valid, in general, but
   nothing in the semantic specification of the language requires that
   all reasoners only perform valid inferences.

If you really stand by this, then there really is no difference in our
positions.  The assumption set, in this case, will include an
assumption that "the algorithm did not err on this occasion."  How
would one check that without reopening the original question?

   You know, Drew, it is slightly irresponsible of you to be airing 
   these old debates in such a forum at this stage in history, IMO.  We 
   have had this battle in AI/KR, and surely we have done it to death 
   and now all understand these matters reasonably well.  If we re-open 
   the procedural/assertional debate now, particularly using the old 
   question-begging terminology of mutual recrimination (neat/scruffy, 
   proceduralist/logicist, etc.) we will NEVER get any useful work done. 

Well, you're certainly right about never getting useful work done.  I
should ration myself to 20 minutes today on these mailing lists.

But I think avoided all those old terms (procedural/assertional et
al.).  Did I slip here or there?  Perhaps I was indulging myself to
think there was something new to say, or a better way to say it to a
fresh audience.

                                   -- Drew McDermott
                                      Yale Computer Science Department

P.S. "The bad old days when people swore vengeance on the bodies of
their rejected conference submissions"?  Those days ended?
Received on Friday, 19 December 2003 21:08:11 UTC

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