■MMMMMMMI cwo PARALLELISM IN AI PROBLEM SOLVING: A CASE STUDY OF HEARSAY II

The Hearsay II speech-understanding system (HSII) (Lesser, et al., 1974; Fennell, 1975; Erman and Lesser, 1975) is an implementation of a knowledge-based multiprocessing Al problem-solving organization. HSII is intended to represent a problem-solving organization which is applu able for implementation in a multiprocessing environment, and is, in particular, currently being implemented on the Cmmp multiprocessor system (Bell, et ai., 1971) at Carnegie-Mellon University. The object of this paper is to explore several of the ramifications of such a problem-solving orgiiniz?tion by examining the mrxhamsms and policies underlying KSH which are necessary for supporting its organization as a multiprocessing problem-solving system. First, an abstract description of a class of problem-solving systems is given using the Production System model of Newell (1973). Then, the HSII problem-solving organization is described in terms of thir model. The various decisions made during the course ot design necessitated the introduction of various multiprocessing mechanisms (e.g., mechanisms for maintaining data localizatior and data integrity), and these mechanisms are discussed. Finally, a simulation -♦■jjy is presented which details the effects of actually implementing such a problem-solving organization for use in a particular application area, thct of speech understanding. This research was supported in part by the Defense Advanced Research Projects Agency of the Office of the Secretary of Defense (Contract F44620-73-C-G074) and monitored by the Air Force Office of Scientific Research I