cess support for formal methods. Model checkers and other finite-state verification tools allow developers to detect certain kinds of errors automatically.Nevertheless, the transition of this technology from research to practice has been slow. While there are a number of potential causes for reluctance to adopt such formal methods, we believe that a primary cause is that practitioners are unfamiliar with specification processes, notations, and strategies. In a recent paper, we proposed a pattern-based approach to the presentation, codification and reuse of property specifications for finite-state verification. Since then, we have carried out a survey of available specifications, collecting over 500 examples of property specifications.We found that most are instances of our proposed patterns. Furthermore, we have updated our pattern system to accommodate new patterns and variations of existing patterns encountered in this survey. This paper reports the results of the survey and the current status of our pattern system.

Finite-state veri cation (e.g., model checking) provides a powerful means to detect errors that are often subtle and di cult to reproduce. Nevertheless, the transition of this technology from research t o p r a c t i c e has been slow. While there are a number of potential causes for reluctance in adopting such formal methods in practice, we believe that a primary cause rests with the fact that practitioners are unfamiliar with speci cation processes, notations, and strategies. Recent y ears have seen growing success in leveraging experience with design and coding patterns. We p r opose a pattern-based approach to the presentation, codi cation and reuse of property speci cations for nite-state veri cation.

Static analysis of concurrent programs has been hindered by the well known state explosion problem. Although many di erent techniques have been proposed to combat this state explosion, there is little empirical data comparing the performance of the methods. This information is essential for assessing the practical value of a technique and for choosing the best method for a particular problem. In this paper, we carry out an evaluation of three techniques for combating the state explosion problem in deadlock detection: reachability search with a partial order state space reduction, symbolic model checking, and inequality necessary conditions. We justify the method used for the comparison, and carefully analyze several sources of potential bias. The results of our evaluation provide valuable data on the kinds of programs to which each technique might best be applied. Furthermore, we believe that the methodological issues we discuss are of general signi cance in comparison of analysis techniques. Keywords| concurrency analysis, empirical evaluation, state space reduction, symbolic model checking, inequality necessary conditions, Ada tasking. 1 This is not the only de nition of deadlock in current use. In particular, some de nitions require a cyclic wait.

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