72. The system according to claim 67 wherein said backward directed reasoning function further comprises: searching for a backward rule to match a first known consequent fact against a rule consequent part node; said backward rule comprising a first set of consequent part nodes, a first set of antecedent part nodes and a first set of context nodes; matching said backward rule consequent part node to said first known consequent fact; then determining a new set of antecedent facts based upon antecedent nodes of an antecedent rule part.
73. The system according to claim 72 wherein said antecedent rule part comprises a disjunction comprising a first set of disjunctive antecedent nodes.