Link PLNDeductionRule(Link LI, Link L2) which calculates the deductive consequence of two links. This function then invokes a function of the form TruthValue PLNDeductionFormula(TruthValue tAB, TruthValue tBC, TruthValue tA, TruthValue tB, Truth which in turn invokes functions such as SimpleTruthValue SimplePLNDeductionFormula(SimpleTruthV