Posted by Paul Chiusano on November 01, 2006 at 14:15:22:
Hi all,
We have lab meeting next week on Tuesday at 3:00. Jordan has suggested
we read and come prepared to discuss a paper by Chris Salzberg which
appeard in the most recent ALife. Here is the full reference:
C. Salzberg. From machine and tape to structure and function:
Formulation of a reflexively computing system, Artificial Life
12(4):487-512, 2006.
And the pdf is at:
http://sacral.c.u-tokyo.ac.jp/~chris/pubs/mt.pdf
The paper describes an alternate model of computation (called
'reflexive computing') which gets away from the usual 'machine and
tape' Turing-machine paradigm, and which might make for a better
ALife/EC substrate than other models of computation that people have
used in the past. (If you saw Charled Ofria's talk, you'll recall that
the 'organisms' were sequences of assembly instructions!) So far I've
just read part of the introduction, but it looks interesting.
Here is the abstract:
The relationship between structure and function is explored via a
system of labeled directed graph
structures upon which a single elementary read/write rule is applied
locally. Boundaries between static (information carrying) and active
(information processing) objects, imposed by mandate of the rules or
physics in earlier models, emerge instead as a result of a
structure-function dynamic that is reflexive: objects may operate
directly on their own structure. Representation of an arbitrary Turing
Machine is reproduced in terms of structural constraints by means of a
simple mapping from tape squares and machine states to a uniform
medium of nodes and links, establishing computation universality.
Exploiting flexibility of the formulation, examples of other
unconventional "self-computing" structures are demonstrated. A
straightforward representation of a kinematic machine system based on
the model devised by Laing [25, 26, 27] is also reproduced in detail.
Implications of the findings are discussed in terms of their relation
to other formal models of computation and construction. It is argued
that reflexivity of the structure-function relationship is a critical
informational dynamic in biochemical systems, overlooked in previous
models but well-captured by the proposed formulation.
Best,
Paul
PS:
Jordan, I hope you don't mind, I just went and found the paper myself
and sent this out...