DARPA ULTRALOG Final Report - Industrial and Manufacturing ...

improving due date performance, increasing quality or reducing costs they become highly
inter-dependent. It is the flow of material, resources, information and finances that
provides the binding force. The well fare of any entity in the system directly depends on
the performance of the others and their willingness and ability to coordinate. This leads to
correlations between entities over long length and time scales.
Figure 1. Supply Chain Network
• Coexistence of Competition and Cooperation: The entities in a supply chain often have
conflicting objectives. Competition abounds in the form of sharing and contention of
resources. Global control over nodes is an exception rather than a rule; more likely is a
localized cooperation out of which a global order emerges, which is itself unpredictable.
• Nonlinear dynamics involving interrelated spatial and temporal effects: Supply
chains have wide geographic distribution. Customers can initiate transactions at any time
with little or no regard for existing load, thus contributing to a dynamic and noisy
network character. The characteristics of a network tend to drift as workloads and
configuration change, producing a non-stationary behavior. The coordination protocols
attempt to arbitrate among entities with resource conflicts. Arbitration is not perfect
however; hence over and under corrections contribute to the nonlinear character of the
network.
• Quasi Equilibrium and combination of regularity and randomness (i.e. interplay of
chaos and non-chaos) The general tendency of a supply chain is to maintain a stable and
prevalent configuration in response to external disturbances. However they can undergo a
radical structural change when they are stretched from equilibrium. At such a point a
small event can trigger a cascade of changes that eventually can lead to system wide
reconfiguration. In some situations unstable phenomena can arise, due to feedback
structure, inherent adjustment delays and nonlinear decision-making processes that go in
the nodes. One of the causes of unstable phenomena is that the information feedback in
the system is slow relative to the rate of changes that occur in the system. The first mode
of unstable behavior to arise in nonlinear systems is usually the simple one-cycle self-