The following functions may be called on instantiations:
which returns the name of the rule of which this is an instantiation.
which returns the list of objects (the token ) which match the rule. These appear in reverse order to the conditions they match.
which returns an a-list of the variables matched in the rule and their values.
KnowledgeWorks and Prolog User Guide (Macintosh version) - 6 Dec 2011