On Feb 8, 2011, at 11:01 PM, Pat Hayes wrote: (01)
>
> On Feb 4, 2011, at 4:03 PM, Rich Cooper wrote:
>
>> Pat, you wrote:
>> In fact, with a bit of extra work one can embed almost all the
>> necessary temporal reasoning into a generalized unification algorithm which
>> extracts temporal constraints during the unification process. I have all the
>> details somewhere if you (or anyone else) are interested.
>>
>> Please do send me the "details" about the "generalized unification algorithm
>> which extracts temporal constraints within the unification process". I am
>> very interested in such material and references.
>
> The only write-up is in a final report to the Army written in 2004. I've put
>a copy here:
>
> http://beta.ihmc.us/users/phayes/Trickledown2004.pdf (02)
Sorry, wrong URI. This should be (03)
http://www.ihmc.us/users/phayes/Trickledown2004.pdf (04)
>
>
> feel free to use it. The Army didn't think enough of it to continue funding
>the project, so its been languishing since then.
>
> Pat
>
>>
>> Thanks for the offer,
>> -Rich
>>
>>
>> Sincerely,
>> Rich Cooper
>> EnglishLogicKernel.com
>> Rich AT EnglishLogicKernel DOT com
>> 9 4 9 \ 5 2 5 - 5 7 1 2
>>
>> -----Original Message-----
>> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Pat Hayes
>> Sent: Thursday, February 03, 2011 1:38 AM
>> To: ian@xxxxxxxxxxxxxxxx; [ontolog-forum]
>> Subject: Re: [ontolog-forum] 3D+1 (was presentism...was blah blah blah)
>>
>> Ian, here's a non-philosophical way to characterize it. Start with an atomic
>> sentence of the form R(a, b), with no time involved, and suppose that a and
>> b here are ordinary uncontroversial physical objects, say. Intuitively, they
>> are 3D things. Now add time, t. Where do we put the time parameter? Several
>> answers can be given.
>>
>> 1. Attach it to the sentence, meaning that the sentence R(a,b) is true at
>> the time t. This gives you a hybrid or context logic where the times are
>> possible temporal worlds/indices or contexts, to which truth is relativized.
>> But the sentences being so relativized do not themselves make any reference
>> to time. Call this 3D.
>>
>> 2. Attach it to the relation as an extra argument, and call the relation a
>> 'fluent': R(a, b, t) This gives you the classical AI/KR approach which used
>> to be called the situation calculus, where one quantifies over times in the
>> KR language itself, but the object terms are still thought of as denoting 3D
>> rather than 4D entities. Call this 3D+1.
>>
>> 3. Attach it to the object terms (using a suitable function, written here as
>> an infix @): R(a@t, b@t) This requires us to make sense of this @ operation,
>> and it seems natural to say that it means the t-slice of the thing named,
>> which now has to be re-thought as a 4D entity. So the a, b things have
>> morphed form being 3D (but lasting through time) to being genuinely 4D, and
>> having temporal slices or parts. Call this 4D.
>>
>> For some folk this last step is apparently mind-boggling, although to me it
>> is puzzling how one can think of something being 3D and also extended in
>> time and have it *not* be 4D. For yet other people (think OBO), there are
>> apparently two kinds of thing in the world, one kind (continuants) which
>> must be described using the 3D+1 style , the other (occurrents) which should
>> be described using the 4D style. God alone knows why anyone would believe
>> that there are two ways to exist in time, but there's nowt as queer as folk,
>> as someone's grandmother used to say.
>>
>> What I like about this way of contrasting the options is that it makes it be
>> simply a matter of syntax - where in the sentence to attach the temporal
>> parameter - and not one of metaphysics. Syntax is way easier than
>> metaphysics. It also means that one can see quite clearly how to make the
>> various formal techniques work together, by allowing the temporal parameter
>> to 'float'. In fact, with a bit of extra work one can embed almost all the
>> necessary temporal reasoning into a generalized unification algorithm which
>> extracts temporal constraints during the unification process. I have all the
>> details somewhere if you (or anyone else) are interested.
>>
>> Pat
>>
>>
>> On Jan 27, 2011, at 11:19 AM, Ian Bailey wrote:
>>
>>> Thanks John,
>>>
>>> So in a 3+1 approach, when they actually "cut some ontology code", if I've
>>> understood you correctly, I'm guessing they timestamp the properties and
>>> relationships ? This contrasts with a 4D approach where the Individual is
>>> sliced up into temporal stages and the properties are associated with the
>>> stages (apart from those properties that apply to the whole-life
>>> individual).
>>>
>>> If I've got that right, then 3+1 is the approach the oil and gas folks
>> used
>>> in late 80s early 90s on EPISTLE and the first drafts of ISO10303-221. Am
>> I
>>> in the right ball park there ? Matthew ?
>>>
>>> Cheers
>>> --
>>> Ian
>>>
>>> -----Original Message-----
>>> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>>> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of John F. Sowa
>>> Sent: 27 January 2011 17:05
>>> To: ontolog-forum@xxxxxxxxxxxxxxxx
>>> Subject: Re: [ontolog-forum] 3D+1 (was presentism...was blah blah blah)
>>>
>>> On 1/27/2011 11:17 AM, Ian Bailey wrote:
>>>> I get 4D, finally, after years of hanging on Chris and
>>>> Matthew's coattails, but the 3D+1 thing is a mystery.
>>>
>>> The basic issue is the definition of a physical object
>>> and its relationship to a privileged time called 'now':
>>>
>>> 1. In 3+1 D, which is the implicit assumption in ordinary
>>> language, an object (human, animal, plant, or artifact)
>>> comes into existence at some time t1 (e.g., birth),
>>> ceases to exist at some time t2 (e.g., death), and
>>> for each now between t1 and t2, all parts of it
>>> exist together now.
>>>
>>> 2. In 4D, a physical object extends over a 4D volume, whose
>>> lower and upper time coordinates are t1 and t2 and whose
>>> spatial coordinates trace out a volume that spans the
>>> object's travels.
>>>
>>> 3, In 3+1 D, the object undergoes various changes, which
>>> cause some properties to become true or false at different
>>> times called now.
>>>
>>> 4. In 4D, the object doesn't change, but it has time-dependent
>>> parts (slices or stages) at which various properties may be
>>> true or false.
>>>
>>> The analogy I prefer (since I studied fluid mechanics at one
>>> time in my life) is between Lagrangian and Eulerian coordinate
>>> systems for representing and computing fluid flow:
>>>
>>> 1. Lagrangian coordinates are like a 3+1 D system: the
>>> observer follows a particular parcel of fluid as it moves.
>>>
>>> 2. Eulerian coordinates are like a 4D system: the observer
>>> sits on the side and watches the flow of all the fluid
>>> as a whole.
>>>
>>> In our ordinary language, we talk about our bodies in Lagrangian
>>> terms. We observe our own motion through space and time, and
>>> relate everything else to where we are *now*.
>>>
>>> An Eulerian system is like a God's eye view of the universe.
>>> God sees everything spread out in all dimensions of space
>>> and time. There is no privileged point of time or space.
>>>
>>> John
>>>
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