Mechanisms for Reasoning about Sets

The SEt Reasoning Facility (SERF) integrates mechanisms for propagating membership propositions, deriving relations between sets, and reasoning about closure and cardinality into an efficient utility package for reasoning about sets. Assertions about relations between sets are compiled into a constraint network defined entirely in terms of union, complement, and emptiness constraints. The constraint network supports multiple modes of inference, such as local propagation of membership propositions and graph search for set relations using a transitivity table. SERF permits closure assertions of the form "all members of set S are known" and utilizes this capability to permit selective applications of closed-world assumptions. Cardinality constraints are handled by a general quantity reasoner. An example from geologic interpretation illustrates the value of mutually constraining sources of information in a typical application of reasoning about sets in commonsense problem-solving.