Signals and Boundaries

Complex adaptive systems (cas), including ecosystems, governments, biological cells,
and markets, are characterized by intricate hierarchical arrangements of boundaries and signals. In
ecosystems, for example, niches act as semi-permeable boundaries, and smells and visual patterns
serve as signals; governments have departmental hierarchies with memoranda acting as signals; and so
it is with other cas. Despite a wealth of data and descriptions concerning different cas, there
remain many unanswered questions about "steering" these systems. In Signals and
Boundaries, John Holland argues that understanding the origin of the intricate
signal/border hierarchies of these systems is the key to answering such questions. He develops an
overarching framework for comparing and steering cas through the mechanisms that generate their
signal/boundary hierarchies.

Holland lays out a path for developing the framework
that emphasizes agents, niches, theory, and mathematical models. He discusses, among other topics,
theory construction; signal-processing agents; networks as representations of signal/boundary
interaction; adaptation; recombination and reproduction; the use of tagged urn models (adapted from
elementary probability theory) to represent boundary hierarchies; finitely generated systems as a
way to tie the models examined into a single framework; the framework itself, illustrated by a
simple finitely generated version of the development of a multi-celled organism; and Markov
processes.