Source : Free On-Line Dictionary of Computing

Delta-Prolog
     
        A {Prolog} extension with {AND-parallelism}, {don't-know
        nondeterminism} and interprocess communication using
        {synchronous event goal}s and {distributed backtracking}.
     
        ["Delta-Prolog: A Distributed Logic Programming Language",
        L.M. Pereira et al, Intl Conf 5th Gen Comp Sys, Nov 1984].