  This chapter reviews four notions of system structure, three of which are
contextual and classic (i.e. the complete computational structure linked to a
state space model, the sparsity pattern of a transfer function, and the
interconnection of subsystems) and one which is relatively new (i.e. the signal
structure of a system's dynamical structure function). Although each of these
structural concepts apply to the nonlinear and stochastic setting, this work
will focus on linear time invariant systems to distill the key concepts and
make their relationships clear. We then discusses three applications of the
newest structural form (the signal structure of a system's dynamical structure
function): network reconstruction, vulnerability analysis, and a recent result
in distributed control that guarantees the synthesis of a stabilizing
controller with a specified structure or proves that no such controller exists.

Systems and Control