Document: Computational Autopoiesis: The Original Algorithm
References
Computational Autopoiesis: The Original Algorithm
5 External Review
The substantive criticisms of (Varela et al. 1974)
presented in this report can be summarised as follows:
- The presented algorithm implements the model
chemistry in a way which is obscure and
counter-intuitive, particularly in relation to the
bonding reaction.
- The algorithm itself is unclear and ambiguous in
places.
- The presented experimental data are not
consistent with the algorithm.
- In fact, it seems likely that the experimental data
actually derived from a program closely related to
that of EXP29.FOR, and thus quite
different in substantial detail from the presented
algorithm.
- By critical consideration of the experimental
results and of the EXP29.FOR code, an
important--perhaps crucial--constraint on the
bonding reaction has been re-discovered: namely
that bonding of free L particles be inhibited
in the immediate vicinity of a chain of such
particles. This interaction can now be clearly
recognised as important to the intended autopoietic
phenomena. However, this interaction has not, to my
knowledge, been explicitly mentioned in any previous
description of the model.
All these defects arise at least in part from the fact
that the target paper dates from the very early days of
this kind of biological modeling. Indeed, the idea of
using this particular form of computational model
should be seen as highly original for its time, and the
authors deserve considerable credit for that. I regard
the concept of autopoiesis, although still somewhat
vague, to be a very useful one in clarifying the
conditions for discussing the origin of life. To this
extent, the concept, and its computational modeling or
realisation, is potentially very significant for the
development of the field of Artificial Life
(Langton 1989).
The criticisms raised here should not be regarded as
detracting from these genuine and important achievements.
Nonetheless: from the point of view of continuing or
developing the particular model presented in the target
paper, these criticisms represent real and serious
obstacles, which need to be overcome. In particular, I
make the following concluding points:
- The discrepancies between the experimental runs
and the given algorithm mean that the demonstration
of basic autopoietic organisation in computational
media claimed by the target paper must be regarded as
weak.
- There are published descriptions of independent
implementations of autopoietic organisation in
computational media
(Zeleny 1977, Zelany & Pierre 1976).
However, I have found the corresponding algorithm
descriptions even more difficult to follow than the
original presented in (Varela et al. 1974). The
corresponding code was made available at the
time, but I understand it is no longer
so.[15]
- As a general principle, the publication of
adequate information to allow independent assessment
and testing of any claims made is a crucial
distinguishing feature of the scientific enterprise.
At the time of original publication of
(Varela et al. 1974) it was neither technically
nor economically feasible to include full source code
with the publication (in machine readable format).
Therefore the authors opted to include a semi-formal
algorithm. This was surely the best practise
possible at the time. However, as we have seen, it
suffers from serious practical deficiencies, and does
not actually meet the desired standard of allowing
independent assessment and testing. Critically, it
seems, in this particular case, that there was an
important interaction present in the code but not
mentioned at all in the description; and this may not
be all that exceptional an occurrence.
- The technology is now available to augment the
use of a published summary, or
algorithm, of model code. At a basic level,
the World Wide Web allows full source code to
be made easily available to any interested
researcher, in machine readable format. At a more
advanced level, the emerging availability of
standardised modeling environments, such as the Swarm
simulation
system[16],
should significantly ease the burden involved in
independent examination and assessment of such
published models.
- I suggest that it would thus be beneficial to
re-implement the original algorithm--and various
related (ideally, simpler) systems modeling the same
qualitative chemistry--to establish how robust, or
otherwise, the autopoietic phenomenology is in these
systems; and it may be especially beneficial to do
this using the Swarm simulation system, and make full
source code of the implementation available via the
World Wide Web. This is the focus of a continuing
research effort, and is the subject of a planned
companion report.
References
Computational Autopoiesis: The Original Algorithm
5 External Review
Document: Computational Autopoiesis: The Original Algorithm
Copyright © 1997 All Rights Reserved.
Timestamp: Tue Dec 31 18:43:32 GMT 1996
mcmullin@eeng.dcu.ie