Pat: (01)
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. (02)
There are so many taxonomies that are used that have no real answer to the
aspect of context. (03)
D (04)
On 6/1/07 12:06 PM, "Pat Hayes" <phayes@xxxxxxx> wrote: (05)
>> 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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> (06)
--
************************************************************
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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