433 research outputs found
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
A Compositional Framework for Preference-Aware Agents
A formal description of a Cyber-Physical system should include a rigorous
specification of the computational and physical components involved, as well as
their interaction. Such a description, thus, lends itself to a compositional
model where every module in the model specifies the behavior of a
(computational or physical) component or the interaction between different
components. We propose a framework based on Soft Constraint Automata that
facilitates the component-wise description of such systems and includes the
tools necessary to compose subsystems in a meaningful way, to yield a
description of the entire system. Most importantly, Soft Constraint Automata
allow the description and composition of components' preferences as well as
environmental constraints in a uniform fashion. We illustrate the utility of
our framework using a detailed description of a patrolling robot, while
highlighting methods of composition as well as possible techniques to employ
them.Comment: In Proceedings V2CPS-16, arXiv:1612.0402
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
Modularizing and Specifying Protocols among Threads
We identify three problems with current techniques for implementing protocols
among threads, which complicate and impair the scalability of multicore
software development: implementing synchronization, implementing coordination,
and modularizing protocols. To mend these deficiencies, we argue for the use of
domain-specific languages (DSL) based on existing models of concurrency. To
demonstrate the feasibility of this proposal, we explain how to use the model
of concurrency Reo as a high-level protocol DSL, which offers appropriate
abstractions and a natural separation of protocols and computations. We
describe a Reo-to-Java compiler and illustrate its use through examples.Comment: In Proceedings PLACES 2012, arXiv:1302.579
Data optimizations for constraint automata
Constraint automata (CA) constitute a coordination model based on finite
automata on infinite words. Originally introduced for modeling of coordinators,
an interesting new application of CAs is implementing coordinators (i.e.,
compiling CAs into executable code). Such an approach guarantees
correctness-by-construction and can even yield code that outperforms
hand-crafted code. The extent to which these two potential advantages
materialize depends on the smartness of CA-compilers and the existence of
proofs of their correctness.
Every transition in a CA is labeled by a "data constraint" that specifies an
atomic data-flow between coordinated processes as a first-order formula. At
run-time, compiler-generated code must handle data constraints as efficiently
as possible. In this paper, we present, and prove the correctness of two
optimization techniques for CA-compilers related to handling of data
constraints: a reduction to eliminate redundant variables and a translation
from (declarative) data constraints to (imperative) data commands expressed in
a small sequential language. Through experiments, we show that these
optimization techniques can have a positive impact on performance of generated
executable code
A System for Distributed Mechanisms: Design, Implementation and Applications
We describe here a structured system for distributed mechanism design
appropriate for both Intranet and Internet applications. In our approach the
players dynamically form a network in which they know neither their neighbours
nor the size of the network and interact to jointly take decisions. The only
assumption concerning the underlying communication layer is that for each pair
of processes there is a path of neighbours connecting them. This allows us to
deal with arbitrary network topologies.
We also discuss the implementation of this system which consists of a
sequence of layers. The lower layers deal with the operations that implement
the basic primitives of distributed computing, namely low level communication
and distributed termination, while the upper layers use these primitives to
implement high level communication among players, including broadcasting and
multicasting, and distributed decision making.
This yields a highly flexible distributed system whose specific applications
are realized as instances of its top layer. This design is implemented in Java.
The system supports at various levels fault-tolerance and includes a
provision for distributed policing the purpose of which is to exclude
`dishonest' players. Also, it can be used for repeated creation of dynamically
formed networks of players interested in a joint decision making implemented by
means of a tax-based mechanism. We illustrate its flexibility by discussing a
number of implemented examples.Comment: 36 pages; revised and expanded versio
Relating BIP and Reo
Coordination languages simplify design and development of concurrent systems.
Particularly, exogenous coordination languages, like BIP and Reo, enable system
designers to express the interactions among components in a system explicitly.
In this paper we establish a formal relation between BI(P) (i.e., BIP without
the priority layer) and Reo, by defining transformations between their semantic
models. We show that these transformations preserve all properties expressible
in a common semantics. This formal relation comprises the basis for a solid
comparison and consolidation of the fundamental coordination concepts behind
these two languages. Moreover, this basis offers translations that enable users
of either language to benefit from the toolchains of the other.Comment: In Proceedings ICE 2015, arXiv:1508.0459
Correlating Formal Semantic Models of Reo Connectors: Connector Coloring and Constraint Automata
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 these models
relate to each other arise. From a theoretical point of view, answers to these
questions provide us with better insight into the fundamentals of Reo, while
from a more practical perspective, these answers broaden the applicability of
Reo's development tools. In this paper, we address one of these questions: we
investigate the equivalence between coloring models and constraint automata,
the two most dominant and practically relevant semantic models of Reo. More
specifically, we define operators that transform one model to the other (and
vice versa), prove their correctness, and show that they distribute over
composition. To ensure that the transformation operators map one-to-one
(instead of many-to-one), we extend coloring models with data constraints.
Though primarily a theoretical contribution, we sketch some potential
applications of our results: the broadening of the applicability of existing
tools for connector verification and animation.Comment: In Proceedings ICE 2011, arXiv:1108.014
Formal Design and Verification of Long-Running Transactions with Extensible Coordination Tools
Distributed splitting of constraint satisfaction problems
Constraint propagation aims to reduce a constraint satisfaction problem into an equivalent but simpler one. However, constraint propagation must be interleaved with a splitting mechanism in order to compose a complete solver. In~cite{monfroy:sac2000 a framework for constraint propagation based on a control-driven coordination model was presented. In this paper we extend this framework in order to integrate a distributed splitting mechanism. This technique has three main advantages: 1),in a single distributed and generic framework, propagation and splitting can be interleaved in order to realize complete distributed solvers, 2), by changing only one agent, we can perform different kinds of search, and 3), splitting of variables can be dynamically triggered before the fixed point of a propagation is reached
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