category theory and rosen - SUMMARY: glen is right to worry 8-)

[Chris Landauer]

glen is basically right in his worries about rosen - there has been much
discussion of the book at a series of semiotics and complexity workshops i
have attended over the last couple of years -

there is no consensus of opinion, and what follows is strictly my own - the
fact that rosen seems to feel the need to _demonstrate_ that biological
systems are not formal means that he does not understand what formal systems
are, despite his use of the words

formal systems are by definition separated from external influences -
everything you can do in them is within them - biological systems, chemical
systems, and any other *real world* system is not so limited - there is
leakage from the context all the time (in fact, that is one unpredictable
source of variation that is exploited continually by biological systems in
evolution)

ok, the diagrams are a useful shorthand, sort of like type declarations, but
they don't actually _do_ anything - especially concerns of independence and
order are important for real systems, because there are very few "point
events"; almost every activity is a process of some kind

of course, as long as you stay within the realm of "abstract block diagrams",
and don't confuse the model with the phenomenon being modeled, rosen is
perfectly all right; he can compose the diagrams at will - however, he cannot
then go and claim correspondence between the composed diagram and the large
system in the real world containing the smaller systems that correspond to the
smaller diagrams -

causality is tricky - it has been a problem for quite a long time, and nobody
has a good definition that is both formally analyzable and easily applicable -
too many people confuse causality with order (a came before b, therefore it
must be that a caused b)

rosen's book is very interesting, but don't trust his use of math

more later,
cal

Dr. Christopher Landauer
Aerospace Integration Science Center
National Systems Group
The Aerospace Corporation
Mail Stop M6/215
P.O.Box 92957
Los Angeles, California 90009-2957
e-mail: address@hidden
Phone: (310) 336-1361


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