Constraint automata have been used as an operational model for Reo which o#ers a channel-based framework to compose complex component connectors. In this paper, we introduce a variant of constraint automata with discrete probabilities and nondeterminism, called probabilistic constraint automata. These can serve for compositional reasoning about connector components, modelled by Reo circuits with unreliable channels, e.g., that might loose or corrupt messages, or channels with random output values that, e.g., can be helpful to model randomized coordination principles.

Reasoning about connector reconfiguration II: basic

Abstract. Architectural styles represent composition patterns and constraints at the software architectural level and are targeted at families of systems with shared characteristics. They enable architectural reuse and hence can bring economy to the design of software architecture. Existing approaches support systematic description of style-based software architectures. Our approach, Alfa, focuses on the construction, instead of description, of style-based software architectures using architectural primitives. This is based on our observation that architectural styles and, indeed, software architectures share many underlying concepts that lead to architectural primitives. Previously, Alfa’s primitives were shown to be sufficient for modeling architectural styles. In this paper, we present the composition of a diverse set of styles for network-based systems using xAlfa, a systematic notation for composing styles from Alfa’s primitives. We then show that two reuse mechanisms in xAlfa, inheritance and composition, enable concise style compositions and unambiguously bring out similarities among architectural styles. 1

CWI is a founding member of ERCIM, the European Research Consortium for Informatics and Mathematics. CWI's research has a theme-oriented structure and is grouped into four clusters. Listed below are the names of the clusters and in parentheses their acronyms.

Coordination and composition of components is an essential concern in component-based software engineering. In this paper, we present an operational semantics for a component composition language called Reo. Reo connectors exogenously compose and coordinate the interactions among individual components, that unawarely comprise a complex system, into a coherent collaboration. The formal semantics we present here paves the way for studying the behavior of component composition mechanisms rigorously. To demonstrate the feasibility of such a rigorous approach, we give a faithful translation of Reo semantics into the Maude term rewriting language. This translation allows us to exploit the rewriting engine and the modelchecking module in the Maude tool-set to symbolically run and model-check the behavior of Reo connectors. 1

Composition of a concurrent system out of components involves coordination of their mutual interactions. In component-based construction, this coordination becomes the responsibility of the glue-code language and its underlying run-time middle-ware. Reo offers an expressive glue-language for construction of coordinating component connectors out of primitive channels. In this paper we consider the problem of synthesizing Reo coordination code from a specification of a behavior as a relation on scheduled-data streams. The specification is given as a constraint automaton that describes the desired input/output behavior at the ports of the components. The main contribution in this paper is an algorithm that generates Reo code from a given constraint automaton.

The complex interactions appearing in service-oriented computing make coordination a key concern in serviceoriented systems. In this paper, we present a fault-based method to generate test cases for component connectors from specifications. For connectors, faults are caused by possible errors during the development process, such as wrongly used channels, missing or redundant subcircuits, or circuits with wrongly constructed topology. We give test cases and connectors a unifying formal semantics by using the notion of design, and generate test cases by solving constraints obtained from the specification and faulty connectors. A prototype symbolic test case generator serves to demonstrate the automatizing of the approach.

Abstract. In software architecture, components represent the computational units of a system and connectors represent the interactions among those units. Making decisions about the semantics of these interactions is a key part of the design process. It is often difficult, however, to choose the appropriate interaction semantics due to the wide range of alternatives and the complexity of the system behavior affected by those choices. Techniques such as finite-state verification can be used to evaluate the impact of these design choices on the overall system behavior. This paper presents the Plug-and-Play approach that allows designers to experiment with alternative design choices of component interactions in a plug-and-play manner. With this approach, connectors representing specific interaction semantics are composed from a library of predefined, reusable building blocks. In addition, standard interfaces for components are defined that reduce the impact of interaction changes on the components ’ computations. This approach facilitates design-time verification by improving the reusability of component models and by providing reusable formal models for the connector building blocks, thereby reducing model-construction time for finite-state verification. 1

Composition of systems out of autonomous subsystems pivots on coordination concerns that center on interaction. Interaction has been studied as an inseparable concern in concurrency theory. Curiously, however, interaction has not been seriously considered as a first-class concept in constructive models of computation. The coordination language Reo provides a powerful and expressive model for flexible composition of behavior through interaction. Reo serves as a good example of a constructive model of computation that treats interaction as a (in fact, the only) first-class concept. It uniquely focuses on the compositional construction of connectors that enable and coordinate the interactions among the constituents in a concurrent system, without their knowledge. We show how Reo allows complex behavior in a system to emerge as a composition of primitive interactions.

Abstract—Reo is a graphical channel-based coordination language that enables the modeling of complex behavioral protocols using a small set of channel types with well-defined behavior. Reo has been developed for the coordination of standalone components and services, which makes it suitable for the modeling of service-based business processes. The formal semantic models for Reo lay the grounds for computer-aided analysis of different aspects of Reo diagrams, including their animation, simulation and verification of control flow and data flow by means of model checking techniques. In this paper, we discuss the verification of data aware Reo process models using the mCRL2 model checking toolset including time analysis. We also show how behavior abstraction can be used to minimize Reo process models and generate smaller mCRL2 specifications. A detailed auction example illustrates our approach to timeaware modeling and verification of data-centric service models. Keywords—formal methods for service-oriented computing; model checking; coordination languages I.