PRISMA: A Mobile Calculus with Parametric Synchronization

2015

The expressiveness of communication primitives has been explored in a common framework based on the π-calculus by considering four features: synchronism (asynchronous vs synchronous), arity (monadic vs polyadic data), communication medium (shared dataspaces vs channel-based), and pattern-matching (binding to a name vs testing name equality vs intensionality). Here another dimension coordination is considered that accounts for the number of processes required for an interaction to occur. Coordination generalises binary languages such as π-calculus to consider languages that can performing joining that combines inputs such as the Join Calculus, splitting that combines outputs; full-coordination that supports both joining and splitting. By means of possi-bility/impossibility of encodings, this paper shows the following results. Coordination is orthogonal to other features and no combination of non-coordination features can encode joining, splitting or full-coordination into a binary la...

FMPPTA, 2001

This paper presents a process calculus for reconfigurable communicating systems which has broadcast as basic communication primitive, and we provide an operational semantics for this calculus. We illustrate the calculus through some examples, and we propose three behavioural equivalences for reasoning about systems of broadcasting processes, namely, barbed equivalence, step-equivalence and labelled bi-similarity. An important result, is that all these relations coincide, providing different ways to study the equivalence/non-equivalence of two systems. Then, we provide a direct characterisation for the strong congruence relation induced by these equivalences. Finally, we give a complete axiomatisation for strong congruence.

Fundamenta Informaticae - FUIN, 2001

Critical issues that arise when process algebras are used for protocol specifications are discussed. To overcome some of these problems, a process algebra for protocol specifications is presented. It is based on Milner's Calculus of Communicating Systems, which is enriched by time and network reasoning. Several bisimulation based semantics for the calculus are defined and their properties are discussed.

1998

The-calculus is a formal model of concurrent computation based on the notion of naming. It has an important role to play in the search for more abstract theories of concurrent and communicating systems. In this paper we augment the-calculus with a constraint store and add the notion of constraint agent to the standard-calculus concept of agent. We call this extension the +-calculus. We also extend the notion of barbed bisimulation to de ne behavioral equivalence for the +-calculus and use it to characterize some equivalent behaviors derived from constraint agents. The paper discusses examples of the extended calculus showing the transparent i n teraction of constraints and communicating processes.

Proceedings of the 2005 ACM symposium on Applied computing - SAC '05, 2005

In this paper we present MoCha-π, an exogenous coordination calculus that is based on mobile channels. A mobile channel is a coordination primitive that allows anonymous point-to-point communication between processes. Our calculus is an extension of the well-known π-calculus. The novelty of MoCha-π is that its channels are a special kind of process that allow other processes to communicate with each other and impose exogenous coordination through user defined channel types. Also new, is the fact that in our calculus channels are viewed as resources. Processes must compete with each other in order to gain access to a particular channel. This makes the calculus more in line with existing systems. An immediate application of this calculus is the modeling of the MoCha middleware, a distributed system that coordinates components using mobile channels.

Theoretical Computer Science, 1985

We present an axiom system ACP, for communicating processes with silent actions ('z-steps'). The system is an extension of ACP, Algebra of Communicating Processes, with Milner's z-laws and an explicit abstraction operator. By means of a model of finite acyclic process graphs for ACP, syntactic properties such as consistency and conservativity over ACP are proved. Furthermore, the Expansion Theorem for ACP is shown to carry over to ACP~. Finally, termination of rewriting terms according to the ACP~ axioms is proved using the method of recursive path orderings.

1997

Components will certainly become a key concept for the next generation of software architectures because of their impact on effective software reuse, real interoperability and integration. Within the Olan project [18], we face the difficulty of defining an operational semantics able to reflect the diversity of execution models involved in real applications. Existing process calculi offer the required abstractions such as encapsulation and process equivalences, but they rely on the fundamental assumption that agents are active, i.e autonomously able to initiate communication. However, components, viewed as software pieces with explicit interfaces, require a notion of passive composition that allows, for instance, several components to be traversed by a same process. In this paper, we introduce a calculus, named ICCS, which extends the Milner's CCS calculus with (1) an operator for passive composition, and (2) selective interactions. While preserving the powerful theory of process equivalences established for CCS, this calculus provides an operational definition of passive components and allows thus to establish the basis of an operational semantics for the Olan Configuration Language.

Electronic Notes in Theoretical Computer Science, 2005

We propose a generalization of synchronization algebras that allows to deal with mobility and local resource handling. We show how it can be used to model communication primitives for distributed and mobile computations, such as the ones used in the global computing area. We propose a graph transformation formalism in the Synchronized Hyperedge Replacement approach which is parametric w.r.t. the synchronization algebra and thus allows to model complex systems based on the chosen communication primitives. We thus unify different models described in the literature and we allow to easily define new ones. We present various examples and a case study on Fusion Calculus, showing how different semantics for it can be derived using different synchronization algebras.

Proceedings of the 2000 ACM symposium on Applied computing - SAC '00, 2000

In this paper we present the σπ coordination language, a core language for specifying dynamic networks of components. The language is inspired by the Manifold coordination language and by the π-calculus. The main concepts of the language are components, classes, objects and channels. A program in σπ consists of a number of components, where each component is a collection of classes separable from its original context and re-usable in any other context. An object is an instance of a class that executes in parallel with the other objects active in the system. The σπ language differs from other models of object-oriented systems mainly in its treatment of communication and mobility: communication is anonymous via synchronous or asynchronous channels, while mobility is obtained by moving channels in the virtual space of linked objects. Thus, a channel is a transferable capability of communication, and objects are mobile in the sense that their communication possibilities may change during a computation. The language σπ itself does not impose exogenous coordination, meaning that the coordination primitives affecting each object can be executed within the computation of the object itself. However, only simple restrictions on the class-definitions of a σπ program suffice to enforce a separation between computation and coordination. Interaction typically occurs anonymously and under the full control of the objects involved. This make it easier to deal with Internet application where security policies must be enforced in view of the possibilities of attacks.

Lecture Notes in Computer Science, 2019

Algebras have always played a critical role in Unifying Theories of Programming, especially in their role in providing the "laws" of programming. The algebraic laws form a triad with two other forms, namely operational and denotational semantics. In this paper we demonstrate that algebras are not just for providing external laws for reasoning about programs. In addition, they can be very beneficial for assisting in the development of theoretical models, most notably denotational semantics. We refer to the algebras used to develop a denotational model as "inner algebras", while the resulting algebraic semantics we consider to be an "outer algebra". In this paper we present a number of inner algebras that arose in the development of a fully compositional denotational semantics, called UTCP, for shared-state concurrency. We explore how these algebras helped to develop (and debug!) the theory, and discuss how they may assist in the ultimate aim of exposing the outer algebra of UTCP, which we expect to be very similar to Concurrent Kleene Algebra.