The Blackboard Model

The blackboard model is the idea that intelligence is orchestration. Developed by Raj Reddy and his colleagues in the Hearsay-II speech understanding system at Carnegie Mellon in the 1970s, it is named after a metaphor its authors found exact: imagine a group of human experts—a phonetician, a linguist, a semanticist, a pragmatist—gathered around a literal blackboard on which a hard problem is written. Each expert watches the board, and whenever they see something they can contribute, they step forward and write it. No one is in charge of the others. No one solves the problem alone. The solution emerges from their opportunistic, independent contributions to a shared workspace. Three components formalize this: the blackboard itself, a shared data structure holding the evolving state of the problem; a set of knowledge sources, independent specialist modules each expert in one aspect; and a control component that decides which knowledge source should act next. The specialists communicate only through