Pitts and Stark have proposed the n-calculus as a language for investigating the interaction of unique name generation and higherorder functions. They developed a sound model based on logical relations, but left completeness as an open problem. In this paper, we develop a complete model based on bisimulation for a labelled transition system semantics. We show that bisimulation is complete, but not sound, for the n-calculus. We also show that by adding assignment to the n-calculus, bisimulation becomes sound and complete. The analysis used to obtain this result illuminates the difficulties involved in finding fully abstract models for n-calculus proper. Keywords: semantics, bisimulation, nominal calculi. 1 Introduction The use of localised information in computing is endemic. In a workplace, where the prevalence of networks and mobile agents is increasing, the concepts of private and public data are of great importance, and the question of how secrecy can be maintained is a significan...

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A prototype version of a semantic-based verification environment for manipulating and analyzing mobile systems specified in the -calculus is presented. In the current version, the -environment provides two main facilities: a -calculus interpreter equipped with a graphical interface, and a verification tool which is used to decide (strong and weak) early and late bisimulation equivalences for finite -calculus processes. The -environment is built on top of existing verification systems, and the re-use of software modules, based on semantical considerations, is the key feature of our proposal. 1 Introduction The -calculus [MPW92] has become the best representative example of mobile process calculi, namely calculi in which the communication topology among processes can dynamically evolve when computation progresses. In the -calculus mobility is achieved via the communication of names rather than communication of processes as happens in so called higher order process calculi (e.g. ...