A Prolog variant with guarded clauses and committed-choice nondeterminism ({don' t-care nondeterminism}) by Ehud "Udi" Shapiro, Yale .A subset has been implemented, but not the full language.See also Mandala.["Concurrent Prolog: Collected Papers", E. Shapiro, V.1-2, MIT Press 1987].(1994-11-30)