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Re: context (comments on http://www.w3.org/TR/2002/WD-rdf-schema-20021112/)

From: Richard H. McCullough <rhm@cdepot.net>
Date: Wed, 4 Dec 2002 09:09:31 -0800
Message-ID: <003c01c29bb7$e9f25b10$bd7ba8c0@rhm8200>
To: "pat hayes" <phayes@ai.uwf.edu>
Cc: "Brian McBride" <bwm@hplb.hpl.hp.com>, <www-rdf-comments@w3.org>
Re: context (comments on http://www.w3.org/TR/2002/My comments are interspersed below, prefixed with #####.
============ 
Dick McCullough 
knowledge := man do identify od existent done
knowledge haspart proposition list

  ----- Original Message ----- 
  From: pat hayes 
  To: Richard H. McCullough 
  Cc: Brian McBride ; www-rdf-comments@w3.org 
  Sent: Tuesday, December 03, 2002 2:22 PM
  Subject: Re: context (comments on http://www.w3.org/TR/2002/WD-rdf-schema-20021112/)


    I have consistently used the same definition of context (http://rhm.cdepot.net/doc/KEtutorial.txt)
        space = where action occurs
    +  time = when action occurs
    +  view = proposition list which captures prior knowledge


  Well, OK, but that is a very odd collection of disparate kinds of thing,  seems to me, which have very little in common (and very little in common with the other uses of that word in other, er, contexts). What is the connection between actions and propositions, for example? 
  ##### Here's a proposition (in KR)
  #####    at space=s, time=t, view=v  { Joe do hit od the ball done }
  ##### This proposition characterizes an action, "hit".  It specifies the subject, "Joe", the object, "the ball", and the context, s/t/v.
  ##### The meaning of this proposition, the things it denotes in reality, is clearly dependent upon the context.  For example: compare space=the local sandlot and space=a major league baseball stadium; compare time=4 December 2002 and time=15 May 1941; compare view={Joe is Joe Doe} and view={Joe is Joe DiMaggio}.  (Of course, view should be a name, and might include many other propositions in addition to the identity/alias given here.)
  And in the first two cases, where are the spatiotemporal boundaries drawn? Take this email conversation that we are having and other people are maybe reading: what is the space where that action is occurring?
  ##### at space=Pioneer California { I do write od this email done }
  ##### at space=your office in Florida { you do read od this email done }
  ##### If you want to consider the complex action/event of all the people reading this email, space=union of all their locations.


    Depending of the context of the discussion, I sometimes emphasized one of space/time/view,
    but my definition has not changed.

    I am fully aware that others do not agree on a definition of context.  You and I attended the same
    Context Symposium at MIT in 1997.


  I recall. Things havn't gotten any better, you know.


  But more seriously, we can't be expected to use *your* definition of context in a language intended for general Web use all over the planet. 
  ##### I don't see why not.  It's based on sound principles.  It works.
  If we try to use a 'general' notion of context we will dissolve into smoke. 
  ##### You're being too pessimistic.
  And in any case, the purely functional requirements of distributed knowledge-processing architecture require that we reduce such contextuality as much as possible. Take your second example, where a sentence's truth depends on the 'context' of the document in which it occurs, 
  ##### There are two parts to the statement from your document.
  ##### 1. Names denote things in the universe.
  ##### 2. Sets of triples denote truth-values.
  ##### We both agree that 1. is true.  Statement 2. is true in your document because you define the denotation of sets of triples to be truth-values.  Statement 2. is false in my document because I define the denotation of sets of triples to be things in the universe (facts of reality).
  and ask yourself what happens when parts of such documents are being distributed across optical fiber, processed, inferences drawn from them, conclusions archived and then re-transmitted arbitrarily long times later, and used in other contexts far from their original source. If meaning depends on contexts which can vanish in microseconds, as they will in the SW, then meaning becomes meaningless.
  ##### Meaning needs to be pinned down with good definitions.


  Pat


    ============
    Dick McCullough
    knowledge := man do identify od existent done
    knowledge haspart proposition list

      ----- Original Message -----
      From: pat hayes
      To: Richard H. McCullough
      Cc: Brian McBride ; www-rdf-comments@w3.org
      Sent: Tuesday, December 03, 2002 12:39 PM
      Subject: Re: context (comments on http://www.w3.org/TR/2002/WD-rdf-schema-20021112/)


        Just two quick comments on context -- stimulated by your previous comments on context.



        1. Context is always important. 



      I might take that comment seriously if I knew what it meant.


        Here's a trivial example.

                Dick McCullough is married.

        In the context of December 2002, this statement is false. 

        In the context of any time between June 1960 and September 1996, it's true.



      No. It was true AT one time but not AT another; or, it was true OF one time but not OF another; or, it is incompletely specified as stated and hence neither true not false, but rather something like a predicate which applies to temporally located entities.




        Here's another example.

                Names denote things in the universe, and sets of triples denote truth-values.

        which is true in the context of your document http://www.w3.org/TR/2002/WD-rdf-mt-20021112/

        but is false in the context of my document http://rhm.cdepot.net/doc/KEtutorial.txt.



      Documents are not contexts in your first sense, and truth is not defined with respect to documents in any case.




        2. Knowledge is advanced by integrating facts into a wider context. 

        For example, in physics,

                force = mass x acceleration

        is a principle which integrates observed facts from many different contexts into a single context. 




      Nonsense. Cite me any physics textbook which refers to such a notion of 'context'.


        By expanding that context to include variable mass and acceleration, we get a broader principle

                force = rate of change of momentum



      Your message illustrates the central problem with the word 'context': it means everything, and so it means nothing. You use it above in three distinct senses which have got nothing whatever to do with one another, and it has been used to mean anything from a single token of a phrase in a particular utterance to an entire culture or human epoch. I have been to maybe six or seven workshops, colloquia, etc., on the topic of 'context' and I don't think I have yet heard two people agree on a definition of the word. On one memorable occasion I listened to talks every hour for 3 working days, and kept careful records, and NONE of them agreed with ANY of the others.  My own considered opinion is that 'context' is a kind of dustbin category, used by people to refer to that part of the problem of specifying meaning they don't yet understand properly.


      If you can come up with something like a definition of what you mean, I would be interested in discussing how to formalize it. Your first sense, which has to do with temporal distinctions, has already been thoroughly analyzed and formally specified.


      Pat


        ============
        Dick McCullough
        knowledge := man do identify od existent done
        knowledge haspart proposition list





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  40 South Alcaniz St.                        (850)202 4416   office
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Received on Wednesday, 4 December 2002 12:09:35 GMT

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