A REIFIED TEMPORAL LOGIC

This paper presents a reified temporal logic for representing and reas oning about temporal and non-temporal relationships between non-tempor al assertions, A clear syntax and semantics for the logic is formally provided. Three types of predicates, temporal predicates, non-temporal predicates and meta-predicates, are introduced. Terms of the proposed language are partitioned into three types, temporal terms, non-tempor al terms and propositional terms. Reified propositions consist of form ulae with each predicate being either a temporal predicate or a meta-p redicate. Meta-predicates may take both temporal terms and proposition al terms together as arguments or take propositional terms alone. A st andard formula of the classical first-order language with each predica te being a non-temporal predicate taking only non-temporal terms as ar guments is reified as just a propositional term. A general time ontolo gy has been provided which can be specialized to a variety of existing temporal systems, The new logic allows one to predicate and quantify over propositional terms while according a special status of time; for example, assertions such as 'effects cannot precede their causes' is ensured in the logic, and some problematic temporal aspects including the delay time between events and their effects can be conveniently ex pressed. Applications of the logic are presented including the charact erization of the negation of properties and their contextual sentences , and the expression of temporal relations between actions and effects .