The synthesis problem for the compositional performance certification of
interconnected systems is considered. A fairly unified description of control synthesis
problem is given using integral quadratic constraints (IQC) and dissipativity. Starting
with a given large-scale interconnected system and a global performance objective, an
optimization problem is formulated to search for admissible dissipativity properties of
each subsystems. Local control laws are then synthesized to certify the relevant
dissipativity properties. Moreover, the term localization is introduced to describe a
finite collection of syntheses problems, for the local subsystems, which are a feasibility
certificate for the global synthesis problem. Consequently, the problem of localizing the
global problem to a smaller collection of disjointed sets of subsystems, called groups, is
considered. This works looks promising as another way of looking at decentralized control
and also as a way of doing performance specifications for components in a large-scale
system.