Summary: The Witness Properties and the Semantics of the Prolog Cut
James H. Andrews
Report No. 542
July 1999
Department of Computer Science
University of Western Ontario
London, Canada
N6A 5B7

Abstract: The semantics of the Prolog ``cut'' construct is explored in the con­
text of some desirable properties of logic programming systems, referred to as the
witness properties. The witness properties concern the operational consistency of
responses to queries. A generalization of Prolog with negation as failure and cut
is described, and shown not to have the witness properties. A restriction of the
system is then described, which preserves the choice and first­solution behaviour of
cut but allows the system to have the witness properties. A static analysis system is
described which allows programs to be computed in a more efficient manner under
the restricted system. The restricted system is then given an abstract semantics,
which depends essentially on the witness properties. Finally, it is shown how the
abstract semantics can be used to simplify proofs of properties of programs.

Source: Andrews, Jamie - Department of Computer Science, University of Western Ontario

Collections: Computer Technologies and Information Sciences