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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: Thu, 5 Dec 2002 11:04:33 -0800
Message-ID: <002001c29c91$26303640$bd7ba8c0@rhm8200>
To: "pat hayes" <phayes@ai.uwf.edu>
Cc: "Brian McBride" <bwm@hplb.hpl.hp.com>, "RDF-Interest" <www-rdf-interest@w3.org>, "Richard S. Latimer" <latimer1@att.net>
Re: context (comments on http://www.w3.org/TR/2002/Note: Per the request of Brian McBride, this ongoing discussion of context has been moved from rdf-comments (concerning current RDF documents) to rdf-interest (concerning future RDF concepts).

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: www-rdf-comments@w3.org 
  Sent: Wednesday, December 04, 2002 9:46 AM
  Subject: Re: context (comments on http://www.w3.org/TR/2002/WD-rdf-schema-20021112/)

    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.)

  Richard, I think you are confused between propositions and worlds. What you are calling the context is just the choice of one interpretation over another. 
  +++++ I'm not confused.  I'm sorry that my comparison of contexts misled you into thinking about "possible worlds".  In the conventional sense, there are no "possible  worlds" and "possible interpretations" in the KR language.  The is only one world -- the world we all live in -- and only one interpretation -- the facts of reality in that one world.  "Possible worlds" only exist in the context of a person's mind, i.e.,
      at view = Pat thinks { ... statements about possible worlds ... }
  Look, the sentence you give here asserts that something - lets say somebody - called Joe hit something called the ball. That is obviously a highly incomplete assertion in that it does not fully specify an entire world. You can fill it out with all kinds of other information about Joe and the ball and where this happened and when and whether or not the sun was shining and the phases of the moon at the time, and whether or not Joe was hungry, and so on and on. There is literally an infinite amount of information you could add to this. All true, and all irrelevant. The fact remains that the sentence itself asserts a proposition which might be true or false in any particular interpretation. The truth of falsity of *other* propositions is irrelevant to that. They are not somehow 'part' of this proposition's 'context', somehow missing and needing to be restored; they are just other propositions that one can put into a representation or not, as one chooses. I can know that Joe hit the ball without knowing anything else about Joe, and that might be all I need or want to know about him.

  Now, it does make sense, I concede, to bundle some of these into something one might want to call the 'context' of an action. But your particular choice of where and when is only the tip of the iceberg here. I know you can ask these questions about the 'context' of an action, since actions always happen at a time and place (well, strictly, that isnt true, but its a handy fiction for most purposes) but you can ask others as well: actions take place in a manner, are done by an agent, to an object, some of them in a direction, some of them for a purpose, and so on. The study of these aspects of action verbs is an entire branch of linguistics. 
  +++++ KR expresses these other aspects of actions in the action statement
      subject do action
          with action characteristics    # e.g. purpose
          out  products                          # output
          od   direct objects                 # input
          from initial characteristics    # e.g. location
          to      final   characteristics    # e.g. location

  So why the two that you have chosen, particularly? 
  +++++ I chose space & time because actions (e.g. walk) are space-time-dependent & attributes (e.g. sex) are not.
  +++++ (Don't bug me about sex-change operations.  KR can handle that.)
  +++++ Note that the same space-time context may apply to many different statements, with the appropriate measurement.  For example, space=New York City, time=1900.
  And I still think that your 'view' doesn't belong with the other two, but is a separate kind of entity. For example, the view might itself have information about the time and place.
  +++++ In general, view will have space-time information.  View names a proposition list, and the propositions may include space-time context.

      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.

  Unioning won't work for distributed things like email conversations. That's why I asked the question. 
  ++++ I don't get your point.  I could have said space=Earth, but that is overgeneralizing.
  Here's a nice example: four people sitting round a table, couples opposite, and each couple is holding a conversation across the table while ignoring the others (sound familiar?) . What is the spatial envelope of each conversation?
  +++++ space=the table.  BTW, I don't know what you mean by "envelope".

        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.

  Im not convinced of either claim. Nothing personal, but this a big topic and I don't trust any simple answers. 
  +++++ Re principles, I have identified the essential characteristics of context.
  +++++ Re working, I have used KR/context very successfully for 6 years, in many different domains.
  But in any case, there is a political aspect to this: even if you were right, how would we get the rest of the world to agree?
  +++++ A serious problem to be sure.  We take it one step at a time, beginning right here with W3C.

      If we try to use a 'general' notion of context we will dissolve into smoke.
      ##### You're being too pessimistic.

  I don't think Im pessimistic at all. I rejoice in the elimination of context.
  +++++ Context can't be eliminated.  As you say below, we can make it explicit.

      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

  No, statement 2 is true *of RDF*, everywhere, because my document is part of the RDF spec. Its the authority of the W3C, backed up maybe by the social assumptions made by the larger culture about what a 'standard' is, that makes it true, ultimately. Truth is not attached or limited to documents, or even defined by documents.
  +++++ Truth is partly defined by documents, in the sense that the documents give definitions of terms which are used to make statements about reality.

       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).

  If your document makes a claim about RDF, then your document is just flat wrong. If on the other hand it makes a claim about some other language, then the two documents are talking about different things. Either way, there is no context involved.
  +++++ You have just identified a key component of context: RDF.  In fact, my document makes no statements about RDF.
  My document talks about the KR language (and the English language).  I tried to bridge the gap between the RDF document and the KR document by associating RDF "sets of triples" with KR "proposition list" with "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.

  Quite; and good definitions will pin down meanings in a noncontextual way, as far as possible. 
  +++++ Definitions, like all other statements, depend on context.
  Archived weather records don't say 'its raining', relying on the context to indicate 'here, now'; they say explicitly where and when it was raining. The added information makes the assertion simply true or false, by encoding the 'context' explicitly in the record. That's the way to make things clear and unambiguous, by getting rid of the context as far as possible. This isn't rocket science, by the way, it has been being done for centuries, probably for millenia. Its likely that this is what writing was originally invented for, in fact.
  +++++ You are not getting rid of the context, you are making it explicit.


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Received on Thursday, 5 December 2002 14:04:42 UTC

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