A Retrospective View of the Hearsay-II Architecture

Abstract

The Hear say mo del ha s been pre sented as a paradigm for a tta cking errorful knowledge-intens ive problems requir ing multiple, cooperating knowledge source s. The Hearsay- JI architecture is the late st attempt to explor e the mode l. This paper describes experience s ga ined while success fully applying thi s architecture to the problem of speech understanding. The major conclusions are : 1. The paradigm of v iewing problem sol ving in terms of hy pothe size - and - t es t actions di s tribut ed among dis tinct repre sentat ions of the problem ha s been shown . to be computationally feasible . 2. A global working mem or y (the "blackboard"), in which the distinct representation s are integrated in a uniform manner, has made it convenient to cons tr uc t and integrate the indi vidual sources of knowledge needed for the proble,;, s olution . 3. The use of a uniform data-directed s tructure for controlling knowledge - source acti v ity has made the system easy to understand and modify. 4. A s olution has been demons trated to the problem of foc usof - attention in thi s type of contro l environment. This s olut ion does not need to be modified when the sources of knowledge in the sy stem are changed.