Stuttering Equivalence and Stuttering Invariance

are not. Stuttering equivalence is a fundamental concept in the theory of concurrent and distributed systems. Notably, Lamport [1] argues that refinement notions for such systems should be insensitive to finite stuttering. Peled and Wilke [2] showed that all PLTL (propositional linear-time temporal logic) properties that are insensitive to stuttering equivalence can be expressed without the next-time operator. Stuttering equivalence is also important for certain verification techniques such as partial-order reduction for model checking. We formalize stuttering equivalence in Isabelle/HOL. Our development relies on the notion of stuttering sampling functions that may skip blocks of identical sequence elements. We also encode PLTL and prove the theorem due to Peled and Wilke [2].