State diagrams

[From Bruce Abbott (951111.1730 EST)]

Bill Powers (951111.1210 MST) --

Bruce Abbott (111195.1230 EST) --
Re: state sets

    ... such [state] diagrams could also document the relationships in
    a sequence-level control system. Different states would define
    different active control systems.

I would say they're more likely to document relationships in a program-
level control system. A sequence is strictly a linear ordered list of
occurrences. There are no tests or choice-points. In a state diagram
like the one you used for illustration, there's at least one implicit
test. Switching to a different state depends on which state you're in
and can be just a sequence, but a time-delay entails a test repeating
until the elapsed time reaches a predetermined value. Only if the device
can operate without any tests at all would it be treatable as a
sequence.

A state diagram would be appropriate for sequences or programs, I would
think. What does it mean to control a sequence? Do we not specify a
sequence of perceptions (produced by control actions), in which bringing the
first in the sequence to reference serves as the condition to start bringing
the second to reference, etc.? If so, then I would think the sequence could
be represented in a state diagram, with the transition from one state to the
next being represented by the perception associated with a given state being
brought to its reference level.

But you say you disagree. Apparently, this whole business about sequences
in HPCT is something I am still very fuzzy about.

Regards,

Bruce