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PatC, PatH,
From the MACK point of view (as that is all I am
capable of...), some comments on your long exchange:
1. You seem to have come (at least
provisionally...) to a happy conclusion on your 3D/4D debate.
Thank you for all the light it has cast on the whole issue.
2. But I cannot help commenting that it took
inordinately long for it to transpire between you that the problem was merely a
syntactic or language-design one, shedding precious little light on the real
semantics of application interoperability and even on how they demand formal
recognition of the time dimensions of data or truths.
3. What a pity that long debate has rather
overshadowed the title of this thread or at least what PatC was trying to
achieve with it! I do hope PatC perseveres with his original point, as I
fully share the intuition behind it, even though confessing to that sentiment
might seem to put me in Azamat's league (so I stress that I do not believe
that the noble conception of a single ultimate reality should translate
into any presumption of a single or fixed human conceptualization of it,
not at any degree of formalization or any level of abstraction).
4. This seems a good point for somebody like
me who so likes to talk of relativity and time to recall some key
background to any so-called 3D/4D or endurantist/perdurantist debate,
namely the predominance in our mental processes and verbal discourse of "things"
and even "states" which endure through time. I even go so far as to insist
that it is not only our very notion of 'identity' which is based on such
continuity of "existence" of "entities": even the very existence or
possibility of life on Earth requires such continuity as the basis of pattern or
predictability despite the chaos of change (or "relative chaos" of a world we
say is governed by the Third Law). That insistence,
incidentally, gives us the conception of the "entity" as the most
basic "otherwise undefined term" of The Mainstream. That our communicable
knowledge can be represented entirely in terms of explicit interrelationships
between such entities is a very basic "axiom", or universalized observation
in The Mainstream Ontology (to coin a phrase on the spur of the moment) which is
presumed obvious or almost going without really needing to be said.
5. But - and this is a big "but" - what we
get out of such observation of continuity is not invariance but covariance, the
very same covariance which expressed Einstein's crucial intuition about physical
(or, more strictly, electromagnetic) law in 1905.
6. Application Interoperation, therefore, is
a matter of covariance: when a message is sent or received (either stage
will do, depending on the context) there has to be a "mutatis mutandis" or
transformation-where-necessary of the contents of the message. Such
transformation must inevitably make explicit some usually implicit
commonality betwwen sender and receiver.
7. And perhaps paradoxically (PatH, you of
all people will surely correct me if I am wrong with this interpretation of it!)
the Frame Problem enters the picture here: the design of that
transformation, as of any state change (for what is a state change but a
transformation too?), emerges in practice from a fine-tuning of Framing
assumptions that have been found to work in the real world.
8. And, PatC, that is where you might perhaps
consider further developing your own intuition as expressed in the subject-line
of this thread? (I for one would certainly look forward to any such
explorations.)
9. However, how MACK deals with the above
issues is based on some very simple observations from real lives and real
distributed applications, from many years ago (first provably disseminated
in 1977 though only quotably written-up in 1984), which I have gradually
elevated to the status of reliably-fixed features of The Mainstream in the
evolution of knowledge as we can usefully conceptualize it at this
stage.
Finally, and as usual from me recently on this
forum, all the above is relevant and - I hope - useful preface to that
too-much-talked-about but not-at-all-mythical "3rd instalment" of my "MACK
basics" series!
So, since it is all rather critical to the
story to come, does anything in it seem to be based on some terrible
misconception? (Or is it really too unclear or verbose - or still too
brief... - for any such to be identifiable?)
Christopher
----- Original Message -----
Sent: Friday, March 21, 2008 1:11
AM
Subject: Re: [ontolog-forum] Ontology
similarity and accurate communication
At 5:47 PM -0400 3/20/08, Patrick Cassidy wrote:
Content-Type:
multipart/alternative;
boundary="----=_NextPart_000_0BC3_01C88AB2.77A87680"
Content-Language:
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PatH,
That¹s a very clear explanation,
thanks much.
I¹ll be looking forward to seeing an
implementation of the logic that has that kind of flexibility.
Well, we can do a lot of this straightforwardly in CLIF, but to really
get hairy one would need a syntactic (and procedural) extension. I worked out
quite a lot of it in a report I did for the Army a few years ago, but we
didn't get a funding renewal, so it never got taken any further. If you are
interested, you can read it here:
http://www.ihmc.us/users/phayes/ARLADA2004Final.pdf
PatH
PatC
Patrick Cassidy
MICRA, Inc.
908-561-3416
cell: 908-565-4053
cassidy@xxxxxxxxx
From:
ontolog-forum-bounces@xxxxxxxxxxxxxxxx
[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Pat
Hayes
Sent: Thursday, March 20, 2008 4:54 PM
To:
[ontolog-forum]
Subject: Re: [ontolog-forum] Ontology similarity
and accurate communication
At 3:35 PM -0400 3/20/08, Patrick Cassidy
wrote:
PatH,
There is an axiom provide by you during this
thread which I would like to
clarify:
>> (forall (x (t Time) P)(iff (P x t)(P (x during t))
))
I have not seen the two different syntactic
expressions:
(P x t) and (P (x
during t))
Used together before. The first suggests a 3D
perspective, and the second
suggests a 4D
perspective.
Yes, exactly. Think of this as a 'bridging'
axiom, part of a translation specification, if you like.
OK, I'll come clean and tell you what I
really think. There are a variety of notational options in combining a
simple timeless assertion with a temporal parameter. One is to treat the
time as a context, in effect attaching it to the entire sentence (or in IKL,
proposition):
(ist t (P x y))
(ist t (that (P x y)))
another is as an extra relational argument,
giving the 'fluent' style which goes naturally with continuants:
(P x y t)
and a third is to connect it to the
object(s) being related, the relation then being naturally understood as a
relation between time-slices:
(P (x at t)(y at t))
But in fact, these are really all just
notational variations on a single theme. They amount to choosing where in
the parse tree of the simple _expression_ to attach the parameter, is all. If
we simply FORGET the philosophy for a second, then we can treat this as an
arbitrary conventional choice, and think of them as all meaning exactly the
same thing, and therefore equivalent. Then it makes literally no difference
if you say "At t, its true that P holds between x and y" or "P is true of x
and y and t" or "P holds between the t-slices of x and y" , as these all
mean the same. As to what exactly x and y are in this, I don't really care
what your favorite philosophical answer is. Choose the philosophy you like
best: but then be prepared to have your head exploded by some of the things
that you might have to read. Maybe this is what you meant by 'dimension
neutral', but I don't like that way of describing it, as I see them myself
as inherently 4-D. Attaching the temporal parameter 'higher up' the tree is
just a handy shorthand convention useful at times; but there are some
things
(Q (x at t)(y at t'))
that just cannot be said any other way. So
we have to have the 4D picture as a kind of base case; and once we have
that, we really don't need the others (all of which are based on highly
questionable philosophical foundations in any case. Trying to make actual
physical sense of the notion of 'continuant' is just about
impossible.)
This is a 'unified' ontology. But note, the
result would not be acceptable to a confirmed 3D modeler; it is for
example incompatible with the OBO foundational ontologies or
DOLCE.
How would you describe the type that "x" belongs
to?
Type?? Do you mean, what kind of thing is it
supposed to denote? Anything with an extension in space and time.
This seems to me to be a basic ontological category. I'd say that if you are
a 3D man, think of it as the union of continuants and occurrents; if a 4D
man, think of it as a 4D 'worm' or history.
The way it is used in those expressions, it looks a lot
like the
"dimension neutral object" that I suggested as a way of
providing both 3D
and 4D perspectives in the same
ontology.
Possibly.
In my case, however, I did not
use the (x during t)
_expression_, but created a type "TimeSlice" so that
time-slices (any
temporal length) of 4D objects could be expressed in an
OWL
formalism.
Oh sure, any 2-argument function is
basically trinary, so has to be re-manipulated to get it into a binary
language like OWL.
Is there a documentation somewhere that
additionally explains the
intended meaning and use of that type (of
which "x" is an instance)?
See above.
PatH
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