A Retrospective View of the Hearsay-II Architecture

Abstract

The Hearsay model has heen presented as a paradigm for attacking errorful knowledge-intensive problems requiring multiple, cooperating knowledge sources. The Hearsay-II architecture is the latest attempt to explore the model. This paper describes experiences gained while successfully applying this architecture to the problem of speech understanding. The major conclusions are: 1. The paradigm of viewing problem solving in terms of hypothesize-and-test actions distributed among distinct representations of the problem has been shown to be computationally feasible. 2. A global working memory (the blackboard), in which the distinct representations are integrated in a uniform manner, has made it convenient to construct and integrate the individual sources of knowledge needed for the problem solution. 3. The use of a uniform data-directed structure for controlling knowledge-source activity has made the system easy to understand and modify. 4. A solution has been demonstrated to the problem of focus-of-attention in this type of control environment. This solution does not need to be modified when the sources of knowledge in the system are changed.