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Abstract. Electronic inter-organizational relationships are governed by contracts regulating their interaction. It is necessary to run-time monitor the contracts, as to guarantee their fulfillment. The present work shows how to obtain a run-time monitor for contracts written in CL, a formal specification language which allows to write conditional obligations, permissions and prohibitions over actions. The trace semantics of CL formalizes the notion of a trace fulfills a contract. We show how to obtain, for a given contract, an alternating Büchi automaton which accepts exactly the traces that fulfill the contract. This automaton is the basis for obtaining a finite state machine which acts as a run-time monitor for CL contracts.

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Abstract. Many long-lived and distributed systems must remain available yet evolve over time, due to, e.g., bugfixes, feature extensions, or changing user requirements. To facilitate such changes, formal methods can help in modeling and analyzing runtime software evolution. This paper presents an executable object-oriented modeling language which supports runtime software evolution. The language, based on Creol, targets distributed systems by active objects, asynchronous method calls, and futures. A dynamic class construct is proposed in this setting, providing an asynchronous and modular upgrade mechanism. At runtime, class redefinitions gradually upgrade existing instances of a class and of its subclasses. An upgrade may depend on previous upgrades of other classes. For asynchronous runtime upgrades, the static picture may differ from the actual runtime system. An operational semantics and a type and effect system are given for the language. The type analysis of an upgrade infers and collects dependencies on previous upgrades. These dependencies are exploited as runtime constraints to ensure type safety.

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