## “Sometimes” and “not never” revisited: On branching versus linear time temporal logic.(English)Zbl 0629.68020

The differences between and appropiateness of branching versus linear time temporal logic for reasoning about concurrent programs are studied. These issues have been previously considered by Lamport. To facilitate a careful examination of these issues, a language, $$CTL^*$$, in which a universal or existential path quantifier can prefix an arbitrary linear time assertion, is defined. The expressive power of a number of sublanguages is then compared. $$CTL^*$$ is also related to the logics MPL of Abrahamson and PL of Harel, Kozen, and Parikh. The paper concludes with a comparison of the utility of branching and linear time temporal logics.

### MSC:

 68N25 Theory of operating systems 68N01 General topics in the theory of software 03B70 Logic in computer science

### Keywords:

parallelism; concurrent programs
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