>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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>Chair - OASIS SOA Reference Model Technical Committee *
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