  This article focuses on the optimization of a complex system which is
composed of several subsystems. On the one hand, these subsystems are subject
to multiple objectives, local constraints as well as local variables, and they
are associated with an own, subsystem-dependent decision maker. On the other
hand, these subsystems are interconnected to each other by global variables or
linking constraints. Due to these interdependencies, it is in general not
possible to simply optimize each subsystem individually to improve the
performance of the overall system. This article introduces a formal graph-based
representation of such complex systems and generalizes the classical notions of
feasibility and optimality to match this complex situation. Moreover, several
algorithmic approaches are suggested and analyzed.
