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Re: [ontolog-forum] Ontology, Information Models and the 'Real World': C

To: Duane Nickull <dnickull@xxxxxxxxx>
Cc: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>, "Barker, Sean (UK)" <Sean.Barker@xxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Sat, 2 Jun 2007 00:22:36 -0700
Message-id: <p06230920c286c5ae18f2@[192.168.1.4]>
>Pat:
>
>You know I have also weighed in heavily in favor of this approach many
>times.  The context aspect strikes me as more than just an object.  It is
>more of a multi faceted qualification framework that overlays any semantic
>or ontological logic.    (01)

Er...thanks, but that is exactly what I'm arguing 
against. That is, contexts do not 'overlay' the 
logic: on the contrary, they are things to be 
described by the logic. The logic is outside, 
describing everything, even the contexts, in a 
uniform context-independent way.    (02)

>
>There are so many taxonomies that are used that have no real answer to the
>aspect of context.    (03)

One of the very basic problems is that there is 
no single notion of "context". (See for example 
http://www.ihmc.us/users/phayes/Pub/ContextsInContext.pdf 
) Which is one reason why we need the flexibility 
of a rich expressive logic to describe the 
various notions and relate them to one another.    (04)

Pat    (05)

>
>D
>
>
>On 6/1/07 12:06 PM, "Pat Hayes" <phayes@xxxxxxx> wrote:
>
>>>  Duane,
>>>  unfortunately, once I get into a 2d environment, I'm not sure
>>>  that "!exists 3d" is meaningful, though it might be in a meta-world
>>>  embedding the 2-d world.
>>>
>>>  Sean Barker
>>>  0117 302 8184
>>>
>>
>>  This message, and indeed this sub-thread,
>>  illustrate perfectly what seems to me to be the
>>  key advantage of using a 'context ontology' (as
>>  IKL does: that is, treating contexts as objects
>>  and making non-contextual assertions about them)
>>  as opposed to a 'context logic' (that is, a logic
>>  in which assertions are understood as being made
>>  in a context and interpreted there using
>>  contextually local criteria). In a word, contexts
>>  in a context logic make meaningful things
>>  meaningless.
>>
>>  Ask yourself: does it make sense to talk of 3-d
>>  things? Yes, of course it does. Are 3-d things of
>>  interest when talking of 2-d things? Yes, of
>>  course they are: they are often the things that
>>  have 2-d surfaces or 2-d projections, for
>>  example. An adequate description of a knife
>>  cutting a block of cheese involves entities of
>>  all dimensions from 4 down (the cutting process
>>  is 4-d; the block is 3-d; the newly revealed
>>  surface of fresh cheese is 2-d and the location
>>  of where the knife edge meets the cheese, where
>>  the action is, is 1-d.) So what advantage or
>>  utility is there is a framework which, when it
>>  talks of 2-d things, makes it incoherent to also
>>  talk of 3-d things? True, we might want to
>>  consider a 'local universe' of purely 2-d
>>  entities: but we can do that (or perhaps, if one
>>  is being a logical purist, can *model* it) by
>>  simply talking about the set of 2-d things -
>>  which amounts, in a classical logic, to having a
>>  property of 2-dimensionality and predicating it
>>  of things in our quantifiers:
>>  (forall ((x 2-D-thing)) ... ) instead of (forall (x) .... )
>>  - and then can make any local assertions about
>>  the 'universe' of 2-d entities that we want.
>>  Nothing is gained by pretending that when we are
>>  "in" (whatever that means) a 2-d context, that
>>  all non-2-d things have some how vanished or
>>  become inaccessible. To think about 2-d entities
>>  is not to enter Flatland: it is simply to be able
>>  to make assertions about a subset of the universe
>>  of discourse.
>>
>>  Pat
>>
>>
>>>
>>>>   -----Original Message-----
>>>>   From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>>>>   [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of
>>>>   Duane Nickull
>>>>   Sent: 31 May 2007 17:10
>>>>   To: [ontolog-forum]
>>>>   Subject: Re: [ontolog-forum] Ontology,Information Models and
>>>>   the 'Real World': Contexts
>>>>
>>>>   Sean:
>>>>
>>>>   Assuming you have modeled correctly, there should logically
>>>>   !exists 3d entity in a 2d environment, should there?
>>>>
>>>>   Duane
>>>>
>>>>
>>>>   On 5/31/07 1:35 AM, "Barker, Sean (UK)"
>>>>   <Sean.Barker@xxxxxxxxxxxxxx> wrote:
>  >>>
>>>>>
>>>>>  What happens if a context/possible world is such that the
>>>>   proposition
>>>>>  ceases to be a proposition? That is, it ceases to evaluate
>>>>   to true or
>>>>>  false? For example, "the volume of a cube is the cube of
>  >>>  the length of
>>>>>  its side" is meaningless in a 2-D world, since there is no
>>>>   concept of
>>>>>  volume. Similarly (A/B > 1) is meaningless in a context
>>>>   where A and B
>>>>>  are both zero.
>>>>>  The tricky part is that there is no order of evaluation in
>>>>   classical
>>>>>  logic, so, in the latter case, adding guards on the
>>>>   context, such as
>>>>>  (A != 0) AND (B != 0), still leaves the combined
>>>>   proposition meaningless.
>>>>>
>>>>>  Sean Barker
>>>>>  0117 302 8184
>>>>>   
>>>>>
>>>>>>  -----Original Message-----
>>>>>>  From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>>>>>>  [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf
>>>>   Of John F.
>>>>>>  Sowa
>>>>>>  Sent: 31 May 2007 02:54
>>>>>>  To: [ontolog-forum]
>>>>>>  Subject: Re: [ontolog-forum] Ontology,Information Models and the
>>>>>>  'Real World': Contexts
>>>>>>
>>>>>>
>>>>>>                 *** WARNING ***
>>>>>>
>>>>>>  This mail has originated outside your organization, either from an
>>>>>>  external partner or the Global Internet.
>>>>>>       Keep this in mind if you answer this message.
>>>>>>
>>>>>>  Wacek, Ken, Pat, Ingvar, et al.,
>>>>>>
>>>>>>  I agree that one should use technical terms in a way that stays
>>>>>>  fairly close to traditional usage.  But the tradition has a lot of
>>>>>>  branches.  In some branches, a proposition is fairly close to a
>>>>>>  sentence, but with the option of considering a restatement in a
>>>>>>  different language to be "the same" proposition.
>>>>>>
>>>>>>  I take that to mean that a proposition is the language-independent
>>>>>>  "meaning" or "intension" of a sentence, and that the truth
>>>>   value is
>>>>>>  evaluated in terms of some "extension" or universe of discourse.
>>>>>>  If somebody changes the extension or universe of
>>>>   discourse, then the
>>>>>>  truth value may change.  But the intension remains fixed.
>>>>>>
>>>>>>  That interpretation is consistent with most 20th-century work on
>>>>>>  modal and other kinds of intensional logics.  Montague,
>>>>   for example,
>>>>>>  defined the intension of a sentence to be a function that maps
>>>>>>  possible worlds to truth values.
>>>>>>  Different possible worlds are different extensions, but
>>>>   the function
>>>>>>  (intension) remains fixed.
>>>>>>
>>>>>>  Although I prefer Dunn's semantics of laws and facts to a
>>>>>>  Kripke-Montague version with possible worlds, Dunn's approach
>>>>>>  produces exactly the same truth values for the same sentences.
>>>>>>  That implies that the same sentence with the same intension
>>>>>>  (proposition) may have different truth values in different
>>>>>>  circumstances.  (I don't care whether anyone chooses to
>>>>  use the terms
>>>>>>  'possible worlds', 'universes of discourse', or 'contexts'
>>>>   for those
>>>>>>  circumstances.)
>>>>>>
>>>>>>  As Ingvar pointed out, Quine requires propositions to have fixed
>>>>>>  truth values.  But that follows from the fact that he does
>>>>   not allow
>>>>>>  different possible worlds or contexts.
>>>>>>
>>>>>>  Although I do not like the notion of possible world, I would agree
>>>>>>  with the modal logicians that any theory of modal logic
>>>>   should permit
>>>>>>  the same intension (proposition) to have different truth values in
>>>>>>  different extensions (universes of discourse).
>>>>>>
>>>>>>  I also agree with Pat that the word 'context' has been used in too
>>>>>>  many confused and confusing ways.  But I don't like either of the
>>>>>>  following ways of talking:
>>>>>>
>>>>>>  KC>> In that sense, a change in context BECOMES a
>>>>>>>>  change in meaning of a proposition
>>>>>>
>>>>>>  PH> No, that is muddled. That is exactly what does NOT happen.
>>>>>>>  A proposition never changes its meaning. The SENTENCE  >
>>>>>>  expresses different propositions.
>>>>>>
>>>>>>  I wouldn't say that a proposition changes its meaning
>>>>   because I would
>>>>>>  prefer to say that a proposition *is* the meaning of a
>>>>   sentence.  I
>>>>>>  also would not say that a sentence whose indexicals were
>  >>>  resolved to
>>>>>>  specific referents could express two or more different
>>>>   propositions.
>>>>>>
>>>>>>  I'm sure that one can find logicians such as Quine who
>>>>   would disagree
>  >>>>> with this interpretation.  But I believe that it is
>>>>   consistent with
>>>>>>  those logicians who are more tolerant of modal logic.  And since I
>>>>>>  want to represent modal sentences in NL, I prefer to accommodate
>>>>>>  their usage (even though I use Dunn's semantics rather than
>>>>>>  Kripke's).
>>>>>>
>>>>>>  John
>>>>>>
>>>>>>   
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>>>>>>
>>>>>>
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>>>>
>>>>   --
>>>>   ************************************************************
>>>>   Sr. Technical Evangelist - Adobe Systems, Inc.             *
>>>>   Chair - OASIS SOA Reference Model Technical Committee      *
>>>>   Blog: http://technoracle.blogspot.com                      *
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>>
>
>--
>************************************************************
>Sr. Technical Evangelist - Adobe Systems, Inc.             *
>Chair - OASIS SOA Reference Model Technical Committee      *
>Blog: http://technoracle.blogspot.com                      *
>My Music: http://www.mix2r.com/audio/by/artist/22ndcentury *
>My Band: http://www.myspace.com/22ndcentury                *
>************************************************************
>
>
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>    (06)


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