Biomedical Engineering Reference
In-Depth Information
Figure 1
. The quadrangle of complex systems. See text.
better-established scientific fields. Having been asked by the editors to describe
its methods and techniques, I begin by explaining what I feel does
not
fall within
my charge, as indicated by Figure 1.
At the top of Figure 1 I have put "patterns." By this I mean more or less
what people in software engineering do (1): a pattern is a recurring theme in the
analysis of many different systems, a cross-systemic regularity. For instance,
bacterial chemotaxis can be thought of as a way of resolving the tension be-
tween the exploitation of known resources, and costly exploration for new, po-
tentially more valuable, resources (Figure 2). This same tension is present in a
vast range of adaptive systems. Whether the exploration-exploitation tradeoff
arises among artificial agents, human decision-makers or colonial organisms,
many of the issues are the same as in chemotaxis, and solutions and methods of
investigation that apply in one case can profitably be tried in another (2,3). The
pattern "tradeoff between exploitation and exploration" thus serves to orient us
to broad features of novel situations. There are many other such patterns in
complex systems science: "stability through hierarchically structured interac-
tions" (4), "positive feedback leading to highly skewed outcomes" (5), "local
inhibition and long-rate activation create spatial patterns" (6), and so forth.
At the bottom of the quadrangle is "foundations," meaning attempts to build
a basic, mathematical science concerned with such topics as the measurement of
