DADO: A Tree-Structured Machine Architecture for Production Systems

Abstract

DAOO (Stolfo and Shaw, 1981) is a parallel, tree-structured machine designed to provide highly significant performance improvements in the execution of production systems. A production system (Newell, 1973; Davis and King 1975; Rychener, 1976) is defined by a set of rules, or productions, which form the production memory (PM), together with a database of assertions, called the working menory (WM). Each production consists of a conjunction of pattern elements, called the left-hand side (LHS) of the rule, along with a set of actions called the right-hand side (RHS). The RHS specifies information which is to be added to (asserted) or removed from WM when the LHS successfully matches against the contents of WM. In this paper, we describe a tree-structured machine architecture that utilizes the emerging technology of VLSI systems in support of the highly efficient parallel execution of large-scale production systans. Portions of the machine, which we have come to call DADO, are now in the early stages of construction at Columbia University. We believe a full-scale DADO prototype, capable of significant performance improvements over implementations based on von Neumann Machines, to be technically and economically feasible for implementation using current technology.