Truth Maintenance System

A truth maintenance system (TMS) is used to record justifications for assertions. Such justifications can be used to generate explanations and to track down the assumptions underlying assertions. In RUP every justification is a disjunctive clause of sentential (propositional) atoms and any such clause can be treated as a justification. RUP’s TMS takes a set of such propositional clauses and performs propositional constraint propagation to ensure that every assertion with a valid justification is in fact believed by the system (thus ensuring a deduction invariant). RUP’s TMS aiso ensures that there is an entry on a contradiction queue for every propositional clause all of whose atoms are false.