We introduce the notion of functional stream derivative, generalising the notion of input derivative of rational expressions (Brzozowski 1964) to the case of stream functions over arbitrary input and output alphabets. We show how to construct Mealy automata from algebraically specified stream functions by the symbolic computation of functional stream derivatives. We illustrate this construction in full detail for various bitstream functions specified in the algebraic calculus of the 2-adic numbers. This work is part of a larger ongoing effort to specify and model component connector circuits in terms of (functions and relations on) streams.

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.

The coordination language Reo supports compositional system construction through connectors with real-time properties that exogenously coordinate the interactions among the constituent components into a coherent collaboration. In this paper, we present an operational semantics for the channel-based component connectors of Reo in terms of Timed Constraint Automata and introduce a temporal-logic for specification and verification of their real-time properties.

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.

Reo is a coordination model based on circuit-like connectors which coordinate components through the interplay of data flow, synchronisation and mutual exclusion, state, and context-dependent behaviour. This paper proposes a scheme based on connector colouring for determining the behaviour of a Reo connector by resolving its context dependent synchronisation and mutual exclusion constraints. Colouring a Reo connector in a specific state with given boundary conditions (I/O requests) provides a means to determine the routing alternatives for data flow. Our scheme has the advantage over previous models in that it is simpler to implement and that it models Reo connectors more closely to their envisaged semantics than existing formal models.

One of the distinguishing features of distributed systems is the importance of the interaction mechanisms that are used to define how the sequential components interact with each other. Given the complexity of the behavior that is being described and the large design space of various alternatives, choosing appropriate interaction mechanisms is difficult. In this paper, we propose a component-based specification approach that allows designers to experiment with alternative interaction semantics. Our approach is also integrated with design-time verification to provide feedback about the correctness of the overall system design. In this approach, connectors representing specific interaction semantics are composed from reusable building blocks. Standard communication interfaces for components are defined to reduce the impact of changing interactions on components ’ computations. The increased reusability of both components and connectors also allows savings at model-construction time for verification. We illustrate our approach by showing how the specification and verification of a small example could be done using the set of building blocks we have defined for message passing. We also show that this set of building blocks can be extended to describe a variety of semantics for other interaction mechanisms such as publish/subscribe and remote procedure call. 1.

Abstract not found

Abstract. As a case study that illustrates our view on coordination and component-based software engineering, we present the design and implementation of a parallel constraint solver. The parallel solver coordinates autonomous instances of a sequential constraint solver, which is used as a software component. The component solvers achieve load balancing of tree search through a time-out mechanism. Experiments show that the purely exogenous mode of coordination employed here yields a viable parallel solver that effectively reduces turn-around time for constraint solving on a broad range of hardware platforms.

Component-based software construction relies on suitable models underlying components, and in particular the coordinators which orchestrate component behaviour. Verifying correctness and safety of such systems amounts to model checking the underlying system model, where model checking techniques not only need to be correct but—since system sizes increase—also scalable and efficient. In this paper, we present a SAT-based approach for bounded model checking of Timed Constraint Automata. We present an embedding of bounded model checking into propositional logic with linear arithmetic, which overcomes the state explosion problem to deal with large systems by defining a product that is linear in the size of the system. To further improve model checking performance, we show how to embed our approach into an extension of counterexample guided abstraction refinement with Craig interpolants.

Abstract Increasingly, complex software systems are being constructed as compositions of reusable software components. One critical issue for such constructions is the design and implementation of the interaction mechanisms, or connectors, that permit the various software components to work together properly. Complex systems also often have extra-functional requirements which these connectors must satisfy. It is not always possible to find an existing connector that satisfies the requirements of the system, and at present it is time-consuming and difficult to create new kinds of connectors. A principled, compositional means of systematically constructing connectors is needed.