Extensions to the Expert System Shell DELFI-2

DELFI-2 is an empty expert system shell designed and developed at Delft University of Technology [1,2]. It has been and still is being used in both industry and institutes for building expert systems and for research on knowledge-based systems. Not unexpectedly, however, one of the intermediate conclusions of research and practical experience with the system has been that it proved to be inadequate, in some circumstances, to apply just one of the available knowledge representation formalisms when building an expert system.