Concurrent Prolog is not efficient in realizing the atomic unification that is the origin of its expressiveness.
At that time, since it was very difficult to judge which of the two languages was better, we planned to pursue both Concurrent Prolog and PARLOG at the same time.
Ehud Shapiro proposed Concurrent Prolog that year, which was a more flexible alternative to Relational Language that featured read-only unification.
* (Concurrent Prolog) The core part of KL1 should be based on Concurrent Prolog, but should support search problems and metaprogramming as well.
While my demonstrations and seminars about LM-Prolog and partial evaluation went well and my discussions with ICOT researchers were productive, the most important event during my visit was my introduction to Concurrent Prolog. Ehud Shapiro, from the Weizmann Institute of Science in Israel was visiting then, working closely with Akikazu Takeuchi of ICOT.
Shapiro and Takeuchi  had written a paper about how Concurrent Prolog could be used as an actor or concurrent object language.
Near the end of 1982, Ehud Shapiro visited ICOT with his idea of Concurrent Prolog (CP).
In Concurrent Prolog: Collected Papers, vol 2, Ehud Shapiro, Ed.
GHC is based on ideas used in Relational Language , Concurrent Prolog
 and Parlog .
In order to get a comparably concise solution in CLP, Shapiro needs to jettison Flat Concurrent Prolog
(his own invention) and introduce us to the super-duper new logic language FCP(arrow pointing up), which is a variant of Saraswat's FCP(arrow pointing down), which is in turn a variant of FCP.
A recent Communications of the ACM article discussed the new concurrent logic language Parlog86, and collected papers on one of the first of these languages, Concurrent Prolog
, have just been these languages, Concurrent Prolog
, have just been published (complete in 1,178 pages) by MIT Press.
This account is not intended to be comparative but pedagogical, so that the features of other concurrent logic programming languages such as Concurrent Prolog
 and GHC  and previous manifestations of Parlog that might confuse the initiate are postponed until the end of the article.