From Tom Bourbon [940629.1731]
I'm just now working my way through the thread on "PCT models" initiated by
Paul George (23 June 1994). Paul cited a 1991 article by Albus, and I
notice that Martin Taylor has copied the article to read. I think a good
place to compare Albus and Powers is in their independently written series
that ran in _BYTE_ magazine, in June, July, August and September, 1979.
Bill Powers wrote about the CST model (as PCT was known back then) and told
how to actually write programs to test the model. Bill's descriptions of
the model and the programs were crystal clear. His programs, hence his
model, actually _worked_ -- a feat that some of you know is of great
significance to the modelers on this net.
In contrast, Albus began the fourth article in his series (which was
titled, "A model of the brain for robot control") by saying, "The
essence of a hierarchy is that control is top-down. The ultimate choices
are made at the top, and the goals selected at this level are decomposed
into action as they filter down through the various levels of the
hierarchy." That's about as far as you can get fvorm the idea about a
control hierarchy in PCT; top-down hierarchies of that kind don't work as
models for living systems. The remainder of the Albus article contained no
working model for a robot, or for a brain. It did contain lots of
speculation and guesses about the furture of robots.
I recommend the two parallel, but widely diverse, series of articles to
anyone who wants to compare the ideas of Powers and Albus.