From liveness to promptness

  • Authors:

  • Orna Kupferman;Nir Piterman;Moshe Y. Vardi

  • Affiliations:

  • Hebrew University, Jerusalem, Israel;Imperial College, London, UK;Rice University, Houston, USA

  • Venue:
  • Formal Methods in System Design
  • Year:
  • 2009

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Abstract

Liveness temporal properties state that something "good" eventually happens, e.g., every request is eventually granted. In Linear Temporal Logic (LTL), there is no a priori bound on the "wait time" for an eventuality to be fulfilled. That is, F 驴 asserts that 驴 holds eventually, but there is no bound on the time when 驴 will hold. This is troubling, as designers tend to interpret an eventuality F 驴 as an abstraction of a bounded eventuality F 驴k 驴, for an unknown k, and satisfaction of a liveness property is often not acceptable unless we can bound its wait time. We introduce here prompt-LTL, an extension of LTL with the prompt-eventually operator F p . A system S satisfies a prompt-LTL formula 驴 if there is some bound k on the wait time for all prompt-eventually subformulas of 驴 in all computations of S. We study various problems related to prompt-LTL, including realizability, model checking, and assume-guarantee model checking, and show that they can be solved by techniques that are quite close to the standard techniques for LTL.