4.2 PIMES INTRINSICS
On the RHS of the Evaluation_of_Features rule, the Boss_Eval and Rib_Eval Check rules are invoked.
It must be noted here that Hypotheses are treated as objects. Each hypothesis object has a single slot with the property name of "Value". The Value slot is of type boolean, which means it can contain a True value or a False value.
Although never spelled out completely, when a hypothesis object is examined by just its name, Nexpert Object presumes to add ".Value". To determine if the Boss_Eval Hypothesis is true, the question is actually "Is Boss_Eval.Value = TRUE". However, Nexpert Object is good enough to do this internally for the programmer to lessen confusion. This is mentioned because, as in PIMES_Setup Hypothesis, the RHS of Evaluation_of_Features forces the evaluation of Boss_Eval.Value by saying
Do Boss_Eval Boss_Eval
As with Session.part_id, there is an attempt to take the message out of the Boss_Eval.Value slot and put it back into the Boss_Eval.Value slot.
There must be rules associated with a hypothesis to determine whether it is true or false. In the case of the Retrieved_Boss hypothesis, there are several rules, all of which are exhaustively evaluated because of the above RHS statement.