CKI Prolog is a small but fine prolog implementation, running under Java with less than optimal, but more than acceptable speed. It was designed to be compatible with Sicstus, SWI and any other prolog implementation. The current edition, beta4 , lacks floating point and DCG, and some (non-essential) predicates are not predefined. CKI prolog can handle operator notation, integer arithmetic, lists, cut and dynamic assert/retract.