Algernon---a tractable system for knowledge-representation

J. M. Crawford, B. J. Kuipers
1991 ACM SIGART Bulletin  
Access-Limited Logic (ALL) is a theory of knowledge representation which formalizes the access limitations inherent in a network structured knowledge-base. Where a deductive method such as resolution would retrieve all assertions that satisfy a given pattern, an access-limited logic retrieves only those assertions reachable by following an available access path. The time complexity of inference in ALL is a polynomial function of the size of the accessible portion of the knowledge-base, rather
more » ... edge-base, rather than an exponential function of the size of the entire knowledge-base (as in much past work). Access-Limited Logic, though incomplete, still has a well de ned semantics and a weakened form of completeness, Socratic Completeness, which guarantees that for any fact which is a logical consequence of the knowledge-base, there is a series of preliminary queries and assumptions after which a query of the fact will succeed. Algernon implements Access-Limited Logic. Algernon is important in testing the claims that common-sense knowledge can be encoded cleanly using access paths, and that in common-sense reasoning the preliminary queries and assumptions can generally be determined from domain knowledge. In this paper we overview the principles of ALL and discuss the application of Algernon to three domains: expert systems, qualitative model building, and logic puzzles.
doi:10.1145/122296.122302 fatcat:mnsgtkuomnaijjv43qvrqf7dmu