Returns an association list of the variables and their bindings in the instantiation. The variables are those produced by the condition part of the forward chaining rule.
For an instantiation of a rule with the precondition
(object ? color ?color-value size ?size)
(inst-bindings inst)
((?color-value . :red) (?size . 20))
KnowledgeWorks and Prolog User Guide (Macintosh version) - 26 Feb 2015