Detecting global predicates in distributed systems with clocks

This paper proposes a framework for predicate detection in systems of processes with approximately-synchronized real-time clocks. Timestamps from these clocks are used to define two orderings on events: "definitely occurred before" and "possibly occurred before". These orderings lead naturally to definitions of 3 distinct detection modalities, i.e., 3 meanings of "predicate Phi held during a computation", namely: POSST Phi ("Phi possibly held"), Def(T) Phi ("Phi definitely held"), and Inst Phi ("Phi definitely held at a specific instant"). This paper defines these modalities and gives efficient algorithms for detecting them; the algorithms are based on algorithms of Cooper and Marzullo, Garg and Waldecker, and Fromentin and Raynal.