We study the relation between specifications of component behaviors and contracts providing means to specify assumptions on environments as well as component guarantees. We show how a contract framework can be built in a generic way on top of any specification theory which supports composition and specification refinement. Our contract framework lifts refinement to the level of contracts and proposes a notion of contract composition on the basis of dominating contracts. Contract composition satisfies a universal property and can be constructively defined if the underlying specification theory is complete, i.e. it offers operators for quotienting and conjoining specifications. We illustrate our generic construction of contracts by moving a specification theory for modal transition systems to contracts and we show that a (previously proposed) trace-based contract theory is an instance of our framework.

Building on the theory of modal I/O automata (MIOs) by Larsen et al. we introduce a new compatibility notion called weak modal compatibility. As an important property of behavioral interface theories we prove that weak modal compatibility is preserved under weak modal refinement. Furthermore, we organize and compare different notions of refinement and compatibility to give an easily-accessible overview. Finally, we describe the MIO Workbench, an Eclipse-based editor and verification tool for modal I/O automata, which implements various refinement, compatibility and composition notions and is able to depict the results of verification directly on the graphical representation of MIOsrelations or state pairs in the positive and erroneous paths in the negative case.

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Global-type formalisms enable to describe the overall behaviour of distributed systems and at the same time to enforce safety properties for communications between system components. Our goal is that of amending a weakness of such formalisms: the difficulty in describing open systems, i.e. systems which can be connected and interact with other open systems. We parametrically extend, with the notion of interface role and interface connection, the syntax of global-type formalisms. Semantically, global types with interface roles denote open systems of communicating finite state machines connected by means of gateways obtained from compatible interfaces. We show that safety properties are preserved when open systems are connected that way. We prefer to use the word role rather then participant since interface role sounds more suitable for the present setting than interface participant.

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