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

From: pat hayes <phayes@ai.uwf.edu>
Date: Wed, 4 Dec 2002 11:46:15 -0600
Message-Id: <p05111b2dba13e7e8e416@[]>
To: "Richard H. McCullough" <rhm@cdepot.net>
Cc: www-rdf-comments@w3.org
>My comments are interspersed below, prefixed with #####.
>Dick McCullough
><http://rhm.cdepot.net/>knowledge := man do identify od existent done
>knowledge haspart proposition list
>----- Original Message -----
>From: <mailto:phayes@ai.uwf.edu>pat hayes
>To: <mailto:rhm@cdepot.net>Richard H. McCullough
>Cc: <mailto:bwm@hplb.hpl.hp.com>Brian McBride ; 
>Sent: Tuesday, December 03, 2002 2:22 PM
>Subject: Re: context (comments on 
>>I have consistently used the same definition of context 
>     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. 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. So why the two that you 
have chosen, particularly? 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 

>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 
>##### 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. 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?

>>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 
>##### 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. 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?

>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.

>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.

>  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.

>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 
>##### 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. 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.


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Received on Wednesday, 4 December 2002 12:46:03 UTC

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