The beast speaks

MIT AI Lab haven't produced anything of value

Forward Reasoning and Dependency-Directed Backtracking in a System for Computer-Aided Circuit analysis by Richard M. Stallman and Gerald J. Sussman
We present a rule-based system for computer-aided circuit analysis. The set of rules, called EL, is written in a rule language called ARS. Rules are implemented by ARS as pattern-directed invocation demons monitoring an associative data base. Deductions are performed in an antecedent manner, giving EL's analysis a catch-as-catch-can flavour suggestive of the behavior of expert circuit analyzers. We call this style of circuit analysis propagation of constraints. The system threads deduced facts with justifications which mention the antecedent facts and the rule used. These justifications may be examined by the user to gain insight into the operation of the set of rules as they apply to a problem. The same justifications are used by the system to determine the currently active data-base context for reasoning in hypothetical situations. They are also used by the system in the analysis of failures to reduce the search space. This leads to effective control of combinatorial search which we call dependency-directed backtracking.

While working (starting in 1975) as a research assistant at MIT under Gerry Sussman,[18] Stallman published a paper (with Sussman) in 1977 on an AI truth maintenance system, called dependency-directed backtracking.[22] This paper was an early work on the problem of intelligent backtracking in constraint satisfaction problems. As of 2009, the technique Stallman and Sussman introduced is still the most general and powerful form of intelligent backtracking.[23] The technique of constraint recording, wherein partial results of a search are recorded for later reuse, was also introduced in this paper.[23]