The HEARSAY-II blackboard
The system was built as a shared blackboard where independent knowledge sources post hypotheses and read each other's, never addressing one another directly.
Why it matters
An architecture for problems where no single source has the whole answer outgrew speech and became a general pattern.
Acoustic, lexical, syntactic and semantic modules run asynchronously and communicate only through the blackboard. Hypotheses carry confidence scores and conflicts are resolved by accumulating evidence. Accuracy reached 90 percent over a thousand-word vocabulary. The blackboard architecture was later used well outside speech, in planning, diagnosis and data fusion.