Program Updating by Incremental and Answer Subsumption Tabling

We propose a novel conceptual approach to program updates implementation that exploits two features of tabling in logic programming (in XSB Prolog): incremental and answer subsumption tabling. Our approach, EVOLP/R, is based on the constructs of Evolving Logic Programs (EVOLP), but simplifies it at first by restricting updates to fluents only. Rule updates are nevertheless achieved via the mechanism of rule name fluents, placed in rules' bodies, permitting to turn rules on or off, through assertions or retractions of their corresponding unique name fluents. Incremental tabling of fluents allows to automatically maintain - at engine level - the consistency of program states. Answer subsumption of fluents addresses the frame problem - at engine level - by automatically keeping track of their latest assertion or retraction. The implementation is detailed here to the extent that it may be exported to other logic programming tabling systems.