1,897 research outputs found
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
Automatic Dynamic Web Service Composition: A Survey and Problem Formalization
The aim of Web service composition is to arrange multiple services into workflows supplying complex user needs. Due to the huge amount of Web services and the need to supply dynamically varying user goals, it is necessary to perform the composition automatically. The objective of this article is to overview the issues of automatic dynamic Web service composition. We discuss the issues related to the semantics of services, which is important for automatic Web service composition. We propose a problem formalization contributing to the formal definition of the pre-/post-conditions, with possible value restrictions, and their relation to the semantics of services. We also provide an overview of several existing approaches dealing with the problem of Web service composition and discuss the current achievements in the field and depict some open research areas
Hybrid Honey Bees Mating Optimization Algorithm for Identifying the Near-Optimal Solution in Web Service Composition
This paper addresses the problem of optimality in semantic Web service composition by proposing a hybrid nature-inspired method for selecting the optimal or near-optimal solution in semantic Web Service Composition. The method hybridizes the Honey-Bees Mating Optimization algorithm with components inspired from genetic algorithms, reinforcement learning, and tabu search. To prove the necessity of hybridization, we have analyzed comparatively the experimental results provided by our hybrid selection algorithm versus the ones obtained with the classical Honey Bees Mating Optimization algorithm and with the genetic-inspired algorithm of Canfora et al
A graph-based framework for optimal semantic web service composition
Web services are self-described, loosely coupled software components that are network-accessible
through standardized web protocols, whose characteristics are described in XML. One of the key
promises of Web services is to provide better interoperability and to enable a faster integration
between systems. In order to generate robust service oriented architectures, automatic composition
algorithms are required in order to combine the functionality of many single services into composite
services that are able to respond to demanding user requests, even when there is no single service
capable of performing such task. Service composition consists of a combination of single services
into composite services that are executed in sequence or in a different order, imposed by a set of
control constructions that can be specified using standard languages such as OWL-s or BPEL4WS.
In the last years several papers have dealt with composition of web services. Some approaches treat
the service composition as a planning problem, where a sequence of actions lead from a initial state
to a goal state. However, most of these proposals have some drawbacks: high complexity, high
computational cost and inability to maximize the parallel execution of web services. Other
approaches consider the problem as a graph search problem, where search algorithms are applied
over a web service dependency graph in order to find a solution for a particular request. These
proposals are simpler than their counterparts and also many can exploit the parallel execution of
web services. However, most of these approaches rely on very complex dependency graphs that
have not been optimized to remove data redundancy, which may negatively affect the overall
performance and scalability of these techniques in large service registries. Therefore, it is necessary
to identify, characterize and optimize the different tasks involved in the automatic service
composition process in order to develop better strategies to efficiently obtain optimal solutions. The
main goal of this dissertation is to develop a graph-based framework for automatic service
composition that generate optimal input-output based compositions not only in terms of complexity
of the solutions, but also in terms of overall quality of service solutions. More specifically, the
objectives of this thesis are: (1) Analysis of the characteristics of services and compositions. The
aim of this objective is to characterize and identify the main steps that are part for the service
composition process. (2) Framework for automatic graph-based composition. This objective will
focus on developing a framework that enables the efficient input-output based service composition,
exploring the integration with other tasks that are part of the composition process, such as service
discovery. (3) Development of optimal algorithms for automatic service composition. This objective
focuses on the development of a set of algorithms and optimization techniques for the generation of
optimal compositions, optimizing the complexity of the solutions and the overall Quality-of-
Service. (4) Validation of the algorithms with standard datasets so they can be compared with other
proposals
A TxQoS-aware business transaction framework
In this thesis, we propose a transaction framework to provide comprehensive and flexible transaction support for contract-driven, service-oriented business processes. The research follows the research method outlined below. Initially, a thorough investigation on current state of affairs was made. Afterwards, we carried out a case study, which we utilized to identify the problems that are likely to occur during the execution of business processes. As the result of the solution design, the concepts, scenarios, life cycles, reference architectures, and mechanisms were proposed to address the problems. The design took place on the conceptual level, while the coding/programming and implementation is out of the scope of this thesis. The business-oriented solution design allows for transaction qualities to be specified and guaranteed by a contractual approach named as TxQoS (Transactional Quality of Service). The technology-oriented design enables flexible composition of ATCs (Abstract Transaction Constructs) as a transaction schema to support the execution of complex processes. As the last step of research, we validated the feasibility of our design by a utility study conducted in a large telecom project, which has complex processes that are service-oriented and contract-driven. Finally, we discussed the contributions and limitations of the research. The main contribution of the thesis is the BTF (Business Transaction Framework) that addresses process execution reliability. The TxQoS approach enables the specification of transaction qualities in terms of FIAT (Fluency, Interference, Alternation, Transparency) properties. This businessfriendly approach allows the providers and users to agree on transaction qualities before process execution time. The building blocks of the proposed framework, ATCs, are reusable and configurable templates, and are abstracted and generalized from existing transaction models. The various transaction requirements of sub-processes and process chunks can be represented by corresponding ATCs, which allow for a flexible composition. Integrated, the TxQoS and ATC approaches work together to form a TxQoS-aware business transaction framework
Quality-constrained routing in publish/subscribe systems
Routing in publish/subscribe (pub/sub) features a communication model where messages are not given explicit destination addresses, but destinations are determined by matching the subscription declared by subscribers. For a dynamic computing environment with applications that have quality demands, this is not sufficient. Routing decision should, in such environments, not only depend on the subscription predicate, but should also take the quality-constraints of applications and characteristics of network paths into account. We identified three abstraction levels of these quality constraints: functional, middleware and network. The main contribution of the paper is the concept of the integration of these constraints into the pub/sub routing. This is done by extending the syntax of pub/sub system and applying four generic, proposed by us, guidelines. The added values of quality-constrained routing concept are: message delivery satisfying quality demands of applications, improvement of system scalability and more optimise use of the network resources. We discuss the use case that shows the practical value of our concept
- …