Finally, system Monitoring and Control operations often work in the reverse direction of primary information flow, and must use reverse protocol styles. Thus, no single option is always best or even attainable. Moreover, each can pose problems. For example, pull protocols cannot deal with unexpected or prioritized events. Push protocols cannot always be buffered effectively, and require the existence or development of scheduling policies and algorithms.
Shared memory requires the overhead of synchronization to avoid storage inconsistencies.
Map out where each policy applies. Center information flow policies on Navigation Models , the components that maintain snapshots of the world. These components are at the point of maximum stress, and bear most responsibility for ensuring that the right values are correctly Updated and propagated. When they are not prespecified, develop the infrastructure components, subsystems, and hardware necessary to support policies. Examine existing similar systems and existing reusable components for guidance in establishing policies.