Two recent projects at ORA have used a blackboard framework during system design.1 DANA is a multimedia network monitoring system, while MARRS is a real-time passive radar system. Both projects have beneted from the AI principles captured in a blackboard design: hierarchically ordered data structures, independent knowledge sources, and intelligent opportunistic control. DANA has proted most by using the knowledge sources to implement a policy of guaranteed update consistency. MARRS has used the independence of knowledge sources and the
exibility of opportunistic control to support quick and easy experimentation with new system designs. This paper presents a new way of incrementally adding opportunistic control to an existing system, and describes several lessons that we learned about the benets and diculties of designing and implementing blackboard systems.
Randall J. Calistri-Yeh