The Free On-line Dictionary of Computing (30 December 2018):

Concurrent Prolog

    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)