Deconstructing

Science of Computer Programming, 2011

Coordination in Reo emerges from the composition of the behavioural constraints of primitives, such as channels, in a component connector. Understanding and implementing Reo, however, has been challenging due to interaction of the channel metaphor, which is an inherently local notion, and the non-local nature of the constraints imposed by composition. In this paper, the channel metaphor takes a back seat. We focus on the behavioural constraints imposed by the composition of primitives and phrase the semantics of Reo as a constraint satisfaction problem. Not only does this provide a clear description of the behaviour of Reo connectors in terms of synchronisation and data flow constraints, it also paves the way for new implementation techniques based on constraint satisfaction. We also demonstrate that this approach is more efficient than existing techniques based on connector colouring. 3

Electronic Notes in Theoretical Computer Science, 2006

We present an operational semantics for a component composition language called Reo. Reo connectors exogenously compose and coordinate the interactions among individual components that comprise a complex system, into a coherent collaboration. The formal semantics we present here paves the way for a rigorous study of the behavior of component composition mechanisms. 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 model-checking module in the Maude tool-set to symbolically run and model-check the behavior of Reo connectors.

Electronic Proceedings in Theoretical Computer Science, 2011

Over the past decades, coordination languages have emerged for the specification and implementation of interaction protocols for communicating software components. This class of languages includes Reo, a platform for compositional construction of connectors. In recent years, various formalisms for describing the behavior of Reo connectors have come to existence, each of them serving its own purpose. Naturally, questions about how

Electronic Notes in Theoretical Computer Science, 2004

In this paper we introduce constraint automata and propose them as an operational model for Reo, an exogenous coordination language for compositional construction of component connectors based on a calculus of channels. By providing composition operators for constraint automata and defining notions of equivalence and refinement relations for them, this paper covers the foundations for building tools to address such concerns as the automated construction of the automaton for a given component connector, equivalence-or containment-checking of the behavior of two given connectors, and verification of coordination mechanisms.

Electronic Notes in Theoretical Computer Science, 2003

In this paper we introduce constraint automata and propose them as an operational model for Reo, an exogenous coordination language for compositional construction of component connectors based on a calculus of channels. By providing composition operators for constraint automata and defining notions of equivalence and refinement relations for them, this paper covers the foundations for building tools to address such concerns as the automated construction of the automaton for a given component connector, equivalence-or containment-checking of the behavior of two given connectors, and verification of coordination mechanisms.

Reo is an exogenous channel-based coordination language that acts as glue code to tie together software components and services. The building blocks of Reo models are connectors that impose constraints on the data-flow in component or service-based architectures in terms of data synchronization, buffering, mutual exclusion, etc. Several semantic models have been introduced to formalize the behavior of Reo. These models differ in terms of expressiveness, computation complexity and purposes that they serve. In this paper, we present a method and a tool for building formal automata-based semantics of Reo that unifies various aspects of existing semantics. We express the behavior of a Reo network as a mixed system of Boolean and numerical constraints constructed compositionally by conjuncting the assertions for its constituent parts. The solutions of this system are found with the help of off-the-shelf constraint solvers and are used to construct the constraint automaton with state memory that gives the sound and complete semantics of Reo with respect to existing models. Our approach is more efficient and scalable compared to the existing methods for generating formal semantics of Reo connectors.

Mathematical Structures in Computer Science, 2004

In this paper, we present Reo, a paradigm for composition of software components based on the notion of mobile channels. Reo is a channel-based exogenous coordination model wherein complex coordinators, called connectors are compositionally built out of simpler ones. The simplest connectors in Reo are a set of channels with well-defined behavior supplied by users. Reo can be used as a language for coordination of concurrent processes, or as a "glue language" for compositional construction of connectors that orchestrate component instances in a component-based system. The emphasis in Reo is on connectors and their composition only, not on the entities that connect to, communicate, and cooperate through these connectors. Each connector in Reo imposes a specific coordination pattern on the entities (e.g., components) that perform I/O operations through that connector, without the knowledge of those entities. Channel composition in Reo is a very powerful mechanism for construction of connectors. We demonstrate the expressive power of connector composition in Reo through a number of examples. We show that exogenous coordination patterns that can be expressed as (meta-level) regular expressions over I/O operations can be composed in Reo out of a small set of only five primitive channel types.

2008 Sixth IEEE International Conference on Software Engineering and Formal Methods, 2008

Reo is an exogenous coordination language for component connectors extending data flow networks with synchronization and context-dependent behavior. We propose an operational model of Reo based on Büchi automata in which port synchronization is modeled by records labeling the transitions, whereas context dependencies are stored in the states. We provide a composition operator which models the joining of two connectors, and show that it can be obtained by using two standard operators: alphabet extension and automata product. Our semantics has the advantage over previous models in that it is based on standard automata theory, so that existing theories and tools can be easily reused. Moreover, it is the first formal model addressing all of Reo's features: synchronization, mutual exclusion, hiding, and context-dependency.

Science of Computer Programming, 2012

Recent approaches to component-based software engineering employ coordinating connectors to compose components into software systems. For maximum flexibility and reuse such connectors can themselves be composed, resulting in an expressive calculus of connectors whose semantics encompasses complex combinations of synchronisation, mutual exclusion, non-deterministic choice and state-dependent behaviour.

Int J Sci Educ, 2004

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.