Information Technology Reference
In-Depth Information
We don't look at their actual code because this is not necessary for our discussion
of creativity in early computer art. Harold Cohen's famous
AARON
started its as-
tonishing career in 1973, and continued to be developed for decades. Frieder Nake's
Generative Aesthetics I
was written, completed, then discarded in the course of one
year, 1968/69.
3.4.1 Harold Cohen:
AARON
AARON is a rule-based system, an enormous expert system, one of the very few
expert systems that ever made it to their productive phase (McCorduck
1990
). In the
end it consisted of so many rules that its sole creator, Cohen, was no longer sure if
he was still capable of understanding well enough their mutual dependencies.
Everything on a computer must be rule-based. A rule is a descriptive element
of the structure:
if
C
then
A
, where
C
is a condition (in the logical sense of
“condition”), and
A
is an action. In the world of computing, a formal definition
must state precisely what is accepted as a
C
, and what is accepted as an
A
.In
colloquial terms, an example could be:
if (figure ahead) then (turn
left or right)
. Of course, the notions of “figure”, “ahead”, “turn”, “left”,
“right” must also be described in computable terms, before this can make any sense
to a computer.
A rule-based system is a collection of interacting rules. Each rule is constructed
as a pair of a condition and an action. The condition must be a description of an event
depending on the state (value) of some variables. It must evaluate to one of the truth-
values
true
or
false
. If its value is
true
, the action is executed. This requires
that its description is also given in computable form. The set of rules making up a
rule-based system may be structured into groups. There must be an order according
to which rules are tested for applicability. One strategy is to apply the first applicable
rule in a given sequence of rules. Another one determines all applicable rules and
selects one of them.
Cohen's AARON worked for many years during which it produced a large col-
lection of drawings. They were first in black and white. Later, Cohen coloured them
by hand according to his own taste or to codes also determined by AARON. The
last stage of AARON relied on a new painting machine. It was constructed such that
it could mimic certain painterly ways of applying paint to paper.
During more than three decades, AARON's command of subjects developed
from collections of abstract shapes to evocations in the observer of rocks, birds, and
plants, and to figures more and more reminiscent of human beings. They gave the
impression of a spatial arrangement, although Cohen never really entered into three
dimensions. A layered execution of figures was sufficient to generate a low-level of
spatial impression.
Around the year 2005, Cohen became somewhat disillusioned with the figural
subjects he had gradually programmed AARON to better and better create. When he
started using computers and writing programs in the early 1970s, he was fascinated
