RE: Processes and Causality

[Chris Partridge <Chris_Partridge@csi.com>]

Dear John,

IMHO one of the 'terms' that should be in the SUO is time. This seems to me
to be a reasonably central notion in most systems. So clarifying what we
mean by it, as you are doing, is important.

In your attachment, you say:
"In summary, time is the set of all possible measurements by a clock, and
space is the set of all possible measurements by a rigid ruler."

I'm not sure I understand completely what you are doing here, and why you
are doing it. It seems to me that the 'possible measurements by a clock'
measure time - but are not time. Similarly for 'possible measurements by a
rigid ruler'. Maybe we need to distinguish between a measurement of time -
e.g. a second - and what is measured. I, maybe like you, feel time and space
are based upon relations between things (and events). One feeling of unease
I have is that your explanation of time (and space) excludes most of the
world's events (and things). It seems to me that every thing is a potential
ruler and every event a potential clock.

This is not to say that the notion of possible clocks and rulers are not
useful in explaining how time and space have a topology and metric.

You say:
"Causality, in David Hume's words, is the cement of the universe that keeps
these measurements consistent and repeatable. It ensures that the ticks of a
clock are regular and that a rigid ruler will give reliable measurements
even after it is moved."

Surely it is the cement that keeps things and events regular and reliable -
and an account of time should respect this intuition.

You go on to say:
"Although the fundamental laws that govern physical processes are stated in
terms of a space-time continuum, they can be
approximated to any desired degree of accuracy by discrete processes
represented as directed acyclic graphs."

Am I to interpret this as saying there is "a space-time continuum" and your
clocks/rulers are meant to explain how we measure it?

Chris

-----Original Message-----
From: owner-standard-upper-ontology@ieee.org
[mailto:owner-standard-upper-ontology@ieee.org]On Behalf Of John F. Sowa
Sent: 27 July 2000 02:52
To: standard-upper-ontology@ieee.org; onto-std@KSL.Stanford.EDU;
cg@cs.uah.edu; sowa@bestweb.net
Subject: Processes and Causality


I finally finished everything but the concluding section of my paper
about causality (which had been triggered by the discussion of the
limitations of the Process Specification Langage, PSL).  The full
paper can be found at

  http://www.bestweb.net/~sowa/ontology/causal.htm

Following is the conclusion of Section 3, in which I compare
several different representations, including Judea Pearl's
causal structures, situation calculus, event calculus, temporal
logic, and PSL.

And by the way, I have been having some problems with my west.poly.edu
e-mail account.  I have therefore decided to switch my primary e-mail
allegiance to sowa@bestweb.net.  Please update any e-mail addresses.

John Sowa