  This paper addresses the decomposition of biochemical networks into
functional modules that preserve their dynamic properties upon interconnection
with other modules, which permits the inference of network behavior from the
properties of its constituent modules. The modular decomposition method
developed here also has the property that any changes in the parameters of a
chemical reaction only affect the dynamics of a single module. To illustrate
our results, we define and analyze a few key biological modules that arise in
gene regulation, enzymatic networks, and signaling pathways. We also provide a
collection of examples that demonstrate how the behavior of a biological
network can be deduced from the properties of its constituent modules, based on
results from control systems theory.
