The valid model semantics for logic programs
Catriel Beeri, Raghu Ramakrishnan, Divesh Srivastava, S. Sudarshan · 1992
We present the valid model semantics, a new approach to providing semantics for logic programs with negation, set-terms and grouping. The valid model semantics is a three-valued semantics, and is defined in terms of a ‘normal form’ computation. The valid model semantics also gives meaning to the generation and use of non-ground facts (i.e., facts with variables) in a computation.