SUO: RE: Discussion Period on Motion by Matthew West
Dear Jon,
See comments below.
Matthew West
Principal Consultant
Shell Information Technology International Limited
Shell Centre, London SE1 7NA, United Kingdom
Tel: +44 20 7934 4490 Other Tel: +44 7796 336538
Email: matthew.west@shell.com
Internet: http://www.shell.com
> -----Original Message-----
> From: Jon Awbrey [mailto:jawbrey@att.net]
> Sent: 02 September 2003 16:22
> To: West, Matthew R SITI-ITPSIE
> Cc: SUO
> Subject: Re: Discussion Period on Motion by Matthew West
>
>
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> JA = Jon Awbrey
> MW = Matthew West
>
> JA: When I think about these things in systems theory terms,
> it always starts with some state space X that contains
> all of the logically possible states of the system you
> want to think about. Your first stab at dealing with
> process will then be in terms of a "path" p : R -> X,
> where R is a real line that you think of as the time
> domain. Physical laws and practical constraints are
> then expressed as subsets of X and subsets of the
> set {p : R -> X} of all possible paths through X.
>
> MW: The states you [describe?] are essentially complex
> properties of a system.
>
> JA: This is where I begin to have trouble making translations
> into a language that I understand. Let me think about a
> state x in a state space X -- some people will be fussy
> here and want to say "configuration space", but because
> I start with non-deterministic systems from the outset
> I don't make that distinction.
>
> MW: So far so good.
>
> JA: One thing that we are talking about when we say "the system"
> is a thing that can be in various states, and a thing that
> can pass through a line or a sequence of states.
>
> MW: Agreed.
>
> JA: In that case, we can say that the state is a complex
> property of this
> system-thing. We say that the system is in the state x
> in the set X,
> and there are projection maps p_j : X -> R, just taking R
> as a typical
> example, and that we think of as "measuring" x in X with
> regard to the
> property corresponding to p_j, and giving us a real number.
>
> MW: I think I'm still with you.
>
> JA: So I think I have a way of understanding the statement that
> a state is just a complex property of a system. Some people
> will call that system-thing the "reified system".
>
> MW: It is that which takes on the state.
>
> Yes, the picky point that I think some people are trying to
> make is that
> the data of experience or the results of measurement are what
> we really
> have on hand, whereas the system-thing is in the bush, as it were, at
> some remove from immediate impressions, the object of possibly many
> and possibly competing hypotheses that we form to explain why the
> data are as they are.
MW: I'm not one of them, as you have probably guessed. As noted below
you can have any individual object you want as long as you can
demonstrate it has a spatio-temporal extent.
>
> JA: They will say that it is nothing but a "hypostatic
> abstraction" that
> personifies the measurements we make and that enter our experience
> and that are the only real things that we ever know of
> this system,
> but I don't see the harm of positing such objects, so long as we
> stay conscious of what we are doing.
>
> MW: One of the things I like about 4-dimensionalism is that
> it is very unfussy
> about what objects there are. If it is some extent in
> space-time, you can
> have it. Why you are interested is up to you. So we are
> allowed systems.
>
> Seems eminently reasonable to me.
>
> MW: The time chunk of the system that possesses the state is
> the relevant
> possible individual, that is itself a temporal part of
> the whole life
> of the system.
>
> JA: Almost. Let me try. Instead of a reified-system-at-an-instant,
> the thing that is in the state x in X, you want to talk about a
> "time chunk" as the thing that has the properties p_j that afford
> a basis for defining the state x in X, along with all of the other
> properties that the system has at that moment?
>
> MW: Sounds good. In the limit it can be reified-system-at-an-instant.
>
> Check.
>
> JA: In practice, both empirical and theoretical practice,
> we commonly approximate continuous trajectories with
> discrete sequences of states, and computational work
> pretty much forces us to start with discrete and even
> finite cases, so it's best to have concepts that cover
> both indifferently, at least, until push comes to shove.
>
> MW: Indeed. I think we have this covered.
>
> Whew!
>
> JA: Given the variety of different ideas about data models
> that we've seen, it might also help if you could say
> a few words about how you see them.
>
> MW: The structure and meaning of data, is the few words version.
> A longer version can be found in:
>
> http://www.matthew-west.org.uk/Documents/princ03.pdf
>
> JA: I could not download or read this successfully,
> and I think my Adobe reader is pretty current.
> Do you have another format?
>
> MW: The site seems to have been having some delays which have made
> connecting and downloading difficult. It seems ok now though.
>
> MW: I have just generated a PDF V1.3 version of the document,
> complete with bookmarks for the TOC. Try that. If it
> still doesn't work I can e-mail it or a Word document.
>
> Will try again.
>
> Jon Awbrey
>
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