3,188 research outputs found
Partially-Distributed Coordination with Reo (Technical Report)
Coordination languages, as Reo, have emerged for the specification and implementation of interaction protocols among concurrent entities. In this paper, we propose a framework for generating partially-distributed, partially-centralized implementations of Reo connectors to improve 1) build-time compilation and 2) run-time throughput and parallelism. Our framework relies on the definition of a new formal product operator on constraint automata (Reo's formal semantics), which enables the formally correct distribution of disjoint parts of a coordination scheme over different machines according to several possible motivations (e.g., performance, privacy, QoS constraints, resource availability, network topology). First, we describe the design and a proof-of-concept implementation of our framework. Then, in a case study, we show and explain how a generated connector implementation can be executed in the Cloud and supports Big Data coordination
Partially distributed coordination with Reo and constraint automata
Algorithms and the Foundations of Software technolog
A distributed computational model for Reo.
The work described in this document aims at producing a formal computational model for the Reo coordination language, that can facilitate the implementation of Reo circuits in a distributed computing environment. The model introduced here partially covers what Reo requires - it implements a less strict form of the merge behavior of mixed nodes. While this already allows computing of a large class of useful circuits, it does not properly deal with some synchronous circuits that contain LossySync channels. This work has lead to a new and more powerful approach to computing the behavior of Reo circuits, called Connector Colorin
Handshaking Protocol for Distributed Implementation of Reo
Reo, an exogenous channel-based coordination language, is a model for service
coordination wherein services communicate through connectors formed by joining
binary communication channels. In order to establish transactional
communication among services as prescribed by connector semantics, distributed
ports exchange handshaking messages signalling which parties are ready to
provide or consume data. In this paper, we present a formal implementation
model for distributed Reo with communication delays and outline ideas for its
proof of correctness. To reason about Reo implementation formally, we introduce
Timed Action Constraint Automata (TACA) and explain how to compare TACA with
existing automata-based semantics for Reo. We use TACA to describe handshaking
behavior of Reo modeling primitives and argue that in any distributed circuit
remote Reo nodes and channels exposing such behavior commit to perform
transitions envisaged by the network semantics.Comment: In Proceedings FOCLASA 2014, arXiv:1502.0315
Toward Sequentializing Overparallelized Protocol Code
In our ongoing work, we use constraint automata to compile protocol
specifications expressed as Reo connectors into efficient executable code,
e.g., in C. We have by now studied this automata based compilation approach
rather well, and have devised effective solutions to some of its problems.
Because our approach is based on constraint automata, the approach, its
problems, and our solutions are in fact useful and relevant well beyond the
specific case of compiling Reo. In this short paper, we identify and analyze
two such rather unexpected problems.Comment: In Proceedings ICE 2014, arXiv:1410.701
Coordination via Interaction Constraints I: Local Logic
Wegner describes coordination as constrained interaction. We take this
approach literally and define a coordination model based on interaction
constraints and partial, iterative and interactive constraint satisfaction. Our
model captures behaviour described in terms of synchronisation and data flow
constraints, plus various modes of interaction with the outside world provided
by external constraint symbols, on-the-fly constraint generation, and
coordination variables. Underlying our approach is an engine performing
(partial) constraint satisfaction of the sets of constraints. Our model extends
previous work on three counts: firstly, a more advanced notion of external
interaction is offered; secondly, our approach enables local satisfaction of
constraints with appropriate partial solutions, avoiding global synchronisation
over the entire constraints set; and, as a consequence, constraint satisfaction
can finally occur concurrently, and multiple parts of a set of constraints can
be solved and interact with the outside world in an asynchronous manner, unless
synchronisation is required by the constraints. This paper describes the
underlying logic, which enables a notion of local solution, and relates this
logic to the more global approach of our previous work based on classical
logic
Distributed Enforcement of Service Choreographies
Modern service-oriented systems are often built by reusing, and composing
together, existing services distributed over the Internet. Service choreography
is a possible form of service composition whose goal is to specify the
interactions among participant services from a global perspective. In this
paper, we formalize a method for the distributed and automated enforcement of
service choreographies, and prove its correctness with respect to the
realization of the specified choreography. The formalized method is implemented
as part of a model-based tool chain released to support the development of
choreography-based systems within the EU CHOReOS project. We illustrate our
method at work on a distributed social proximity network scenario.Comment: In Proceedings FOCLASA 2014, arXiv:1502.0315
Connectors meet Choreographies
We present Cho-Reo-graphies (CR), a new language model that unites two
powerful programming paradigms for concurrent software based on communicating
processes: Choreographic Programming and Exogenous Coordination. In CR,
programmers specify the desired communications among processes using a
choreography, and define how communications should be concretely animated by
connectors given as constraint automata (e.g., synchronous barriers and
asynchronous multi-casts). CR is the first choreography calculus where
different communication semantics (determined by connectors) can be freely
mixed; since connectors are user-defined, CR also supports many communication
semantics that were previously unavailable for choreographies. We develop a
static analysis that guarantees that a choreography in CR and its user-defined
connectors are compatible, define a compiler from choreographies to a process
calculus based on connectors, and prove that compatibility guarantees
deadlock-freedom of the compiled process implementations
Treo: Textual Syntax for Reo Connectors
Reo is an interaction-centric model of concurrency for compositional
specification of communication and coordination protocols. Formal verification
tools exist to ensure correctness and compliance of protocols specified in Reo,
which can readily be (re)used in different applications, or composed into more
complex protocols. Recent benchmarks show that compiling such high-level Reo
specifications produces executable code that can compete with or even beat the
performance of hand-crafted programs written in languages such as C or Java
using conventional concurrency constructs.
The original declarative graphical syntax of Reo does not support intuitive
constructs for parameter passing, iteration, recursion, or conditional
specification. This shortcoming hinders Reo's uptake in large-scale practical
applications. Although a number of Reo-inspired syntax alternatives have
appeared in the past, none of them follows the primary design principles of
Reo: a) declarative specification; b) all channel types and their sorts are
user-defined; and c) channels compose via shared nodes. In this paper, we offer
a textual syntax for Reo that respects these principles and supports flexible
parameter passing, iteration, recursion, and conditional specification. In
on-going work, we use this textual syntax to compile Reo into target languages
such as Java, Promela, and Maude.Comment: In Proceedings MeTRiD 2018, arXiv:1806.0933
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