Applying intelligent agents and semantic web services in eGovernment environments

The increasing volume of eGovernment‐related services is demanding new approaches for service integration and interoperability in this domain. Semantic web (SW) technologies and applications can leverage the potential of eGovernment service integration and discovery, thus tackling the problems of semantic heterogeneity characterizing eGovernment information sources and the different levels of interoperability. eGovernment services will therefore be semantically described in the foreseeable future. In an environment with semantically annotated services, software agents are essential as the entities responsible for exploiting the semantic content in order to automate some tasks, and so enhance the user's experience. In this paper, we present a framework that provides a seamless integration of semantic web services and intelligent agents technologies by making use of ontologies to facilitate their interoperation. The proposed framework can assist in the development of powerful and flexible distributed systems in complex, dynamic, heterogeneous, unpredictable and open environments. Our approach is backed up by a proof‐of‐concept implementation, where the breakthrough of integrating disparate eGovernment services has been tested.     

METEOR-S WSDI: A Scalable P2P Infrastructure of Registries for Semantic Publication and Discovery of Web Services

Web services are the new paradigm for distributed computing. They have much to offer towards interoperability of applications and integration of large scale distributed systems. To make Web services accessible to users, service providers use Web service registries to publish them. Current infrastructure of registries requires replication of all Web service publications in all Universal Business Registries. Large growth in number of Web services as well as the growth in the number of registries would make this replication impractical. In addition, the current Web service discovery mechanism is inefficient, as it does not support discovery based on the capabilities of the services, leading to a lot of irrelevant matches. Semantic discovery or matching of services is a promising approach to address this challenge. In this paper, we present a scalable, high performance environment for Web service publication and discovery among multiple registries. This work uses an ontology-based approach to organize registries into domains, enabling domain based classification of all Web services. Each of these registries supports semantic publication and discovery of Web services. We believe that the semantic approach suggested in this paper will significantly improve Web service publication and discovery involving a large number of registries. This paper describes the implementation and architecture of the METEOR-S Web Service Discovery Infrastructure, which leverages peer-to-peer computing as a scalable solution.     

EASY: Efficient semAntic Service discoverY in pervasive computing environments with QoS and context support

Pervasive computing environments are populated with networked software and hardware resources providing various functionalities that are abstracted, thanks to the Service Oriented Architecture paradigm, as services. Within these environments, service discovery enabled by service discovery protocols (SDPs) is a critical functionality for establishing ad hoc associations between service providers and service requesters. Furthermore, the dynamics, the openness and the user-centric vision aimed at by the pervasive computing paradigm call for solutions that enable rich, semantic, context- and QoS-aware service discovery. Although the semantic Web paradigm envisions to achieve such support, current solutions are hardly deployable in the pervasive environment due to the costly underlying semantic reasoning with ontologies. In this article, we present EASY to support efficient, semantic, context- and QoS-aware service discovery on top of existing SDPs. EASY provides EASY-L, a language for semantic specification of functional and non-functional service properties, as well as EASY-M, a corresponding set of conformance relations. Furthermore, EASY provides solutions to efficiently assess conformance between service capabilities. These solutions are based on an efficient encoding technique, as well as on an efficient organization of service repositories (caches), which enables both fast service advertising and discovery. Experimental results show that the deployment of EASY on top of an existing SDP, namely Ariadne, enhancing it only with slight changes to EASY-Ariadne, enables rich semantic, context- and QoS-aware service discovery, which furthermore performs better than the classical, rigid, syntactic matching, and improves the scalability of Ariadne.     

基于历史调用日志分析的Web服务间语义相关性发现

针对Web服务间语义相关性发现这一Web服务领域研究的关键问题,目前的方法不能较好地描述服务间语义相关的不确定性,进而不能有效地支持自动服务发现与组合.以Web服务描述中的操作作为服务组件,首先给出Web服务调用历史日志的定义,接着以统计计算为手段,基于PageRank算法给出服务组件权重的计算方法,进一步基于静电场理论给出Web服务组件间语义相关度的度量方法,为Web服务搜索、发现与组合奠定基础.实验结果表明,该方法具有高效性和实用性.     

基于XQuery扩展的异构语义Web服务发现

语义Web服务发现作为分布式计算的前提和关键,备受研究者关注。多种语义Web服务描述语言的存在给异构语义Web服务的发现带来了挑战。本文提出了一种支持异构语义Web服务描述语言的发现框架i XQuery。该框架从两个方面扩展XQuery,使其支持异构语义Web服务的结构化查询与逻辑推理、模糊匹配的联合查询。一方面i XQuery利用XQuery的外部函数机制,建立了多种类型的相似度比较函数;另一方面i XQuery制定了一个统一的语义Web服务抽象描述本体,并建立了语义Web服务语言SAWSDL与OWLS与该本体之间的映射,并利用XQuery的用户自定义函数机制,建立了一系列用于抽取异构语义Web服务中信息的抽象描述操作子。最后,介绍了基于i XQuery框架的异构语义Web服务匹配器H-i Matcher。     

一种基于本体和Agent的网格服务发现机制

在动态的网格计算环境中分布着大量不同类型的网格服务。快速、准确地进行网格服务发现是影响网格计算性能的关键因素。本文提出了基于本体和Agent的网格服务发现机制,它具有良好的扩展性和完备性。该模型采用Agent代理技术进行服务搜索,不同的代理能够提供不同虚拟组织的本体知识库;利用本体论语义进行服务的匹配,从而实现智能化的服务发现。     

A semantic service discovery approach for ubiquitous computing

Services in the ubiquitous computing are heterogeneous in nature. To be pervasive, these services should be defined in terms of their functionality and capabilities rather than the meaningless Universally Unique IDentifiers (UUIDs) or types of services. With that, clients can access the proper service based on semantic requests, rather then a pre-configured profile. In this paper, we study the requirements for semantic query to be feasible in service discovery processes. Current discovery protocols and the concept of semantics are brought together to construct a framework to realize the semantic service discovery for ubiquitous computing. Many issues are discussed in relation to service discovery topologies, ontology languages, and semantic query languages.     

Facilitating Service Discovery with Semantic Overlay

Service Oriented Architecture （SOA） and Peer-to-Peer （P2P） computing share many common characteristics. It is believed that the combination of the two emerging techniques is a very promising method in promoting the web services （WS）. Because the service discovery plays a key role in the integration, here a P2P-based framework to manage the knowledge of service and locating services is proposed. In this paper, the details of the principle, constructing and maintaining of service semantic overlay architecture have been described, and the way how the semantic overlay facilitates discovery of service resources is illustrated. To enable the semantic web service superiority, Service Ontology, which is considered as the service semantic model, is employed to depict service. The service discovery includes two phases： searching on the service semantic overlay; and local discovery in peer＇s service repository. Various solutions have been proposed to realize those two phases. Furthermore, tests are carried out to evaluate service discovery on the architecture.     

Implementing a Semantic Service Provision Platform

Seamless integration of information systems plays a key role in the development and maintenance of products. In today’s dynamic market environments, change is the rule rather than the exception. Consequently, the ability to change products is an effective way to adapt to a changing information technology landscape which is an important competitive advantage of a successful company. The vision of service-oriented computing is to capture business relevant functionalities of existing software systems as services and use service composition to form composite applications. Unfortunately, this vision has yet to be achieved. We present here a high-level overview of a semantic service discovery, composition, and enactment system that realizes this vision. Rather than addressing a fully fledged industrial strength system, we present a research prototype that realizes this vision in a narrow application domain to show the general feasibility of automatic semantic discovery, composition and flexible enactment of services. The lessons we learned from implementing this prototype are: a) The requirements regarding the features of logical reasoners for the implementation of “real” scenarios are high. b) A formal and exact specification of the semantics of “real world” services is a laborious task. c) It is hard to find adequate scenarios, because people don’t trust this technology and they don’t like to give the control on business processes to a machine, because questions like “Who is responsible?” arise. Furthermore, the application of automated and flexible service discovery and composition at run-time is only cost-effective if changes and volatilities are frequent in the service landscape.     

Service discovery 101

A key aspect of the service-oriented architecture approach for middleware is that services advertise themselves using directory or lookup services so that prospective clients can find them. The service location and discovery abstractions required to support this are not much different from those we use to conduct business with other people. As a result, we can gain insights into how distributed service discovery systems work by comparing them to everyday human-oriented service discovery approaches. Given that service discovery depends on discovery services, how does an application actually find a discovery service?.     

Composing web services enacted by autonomous agents through agent-centric contract net protocol

ContextAgents are considered as one of the fundamental technologies underlying open and dynamic systems that are largely enabled by the semantic web and web services. Recently, there is a trend to introduce the notion of autonomy empowered by agents into web services. However, it has been argued that the characteristics of autonomy will make agents become available intermittently and behave variedly over time, which therefore increase the complexity on devising mechanisms for composing services enacted by autonomous agents.ObjectiveIn this work, we propose an extension to Contract Net protocol, called Agent-centric Contract Net Protocol (ACNP), as a negotiation mechanism with three key features for composing web services enacted by autonomous agents.Method(1) A matchmaking mechanism embedded in a middle agent (as a service matchmaker) for discovering web services that are available intermittently is presented based on the concept of agent roles; (2) A selection algorithm based on risk-enabled reputation model (REAL) embedded in a manager agent (as a service composer) is introduced to serve a basis for selecting web services with variant performance; and (3) A negotiation mechanism between a manager agent and contractor agents (as atomic services) is devised and enables both a service composer and the atomic services to request, refuse or agree on adapting changes of services.ResultsThe problem of assembling a computer is discussed in this paper.ConclusionIt is increasingly recognised that web services would become more autonomous by introducing diverse agent technologies to better constitute more complex systems in open and dynamic environments. As web service technologies are best exploited by composite services, it is imperative to devise mechanisms for composing services of autonomy.     

一种基于情境的语义Web服务发现方法

在普适计算环境下,如何结合情境信息以发现满足用户需求的服务,是目前Web服务研究的一个关键问题.提出一种基于情境的Web服务发现框架,采用本体进行情境建模,利用用户反馈信息进行权重计算,并给出了一个基于相似度的语义Web服务的匹配算法.最后通过实验验证了该方法的有效性.     

COCOA: COnversation-based service COmposition in pervAsive computing environments with QoS support

Pervasive computing environments are populated with networked services, i.e., autonomous software entities, providing a number of functionalities. One of the most challenging objectives to be achieved within these environments is to assist users in realizing tasks that integrate on the fly functionalities of the networked services opportunely according to the current pervasive environment. Towards this purpose, we present COCOA, a solution for COnversation-based service COmposition in pervAsive computing environments with QoS support. COCOA provides COCOA-L, an OWL-S based language for the semantic, QoS-aware specification of services and tasks, which further allows the specification of services and tasks conversations. Moreover, COCOA provides two mechanisms: COCOA-SD for the QoS-aware semantic service discovery and COCOA-CI for the QoS-aware integration of service conversations towards the realization of the user task’s conversation. The distinctive feature of COCOA is the ability of integrating on the fly the conversations of networked services to realize the conversation of the user task, by further meeting the QoS requirements of user tasks. Thereby, COCOA allows the dynamic realization of user tasks according to the specifics of the pervasive computing environment in terms of available services and by enforcing valid service consumption.     

一种双层P2P结构的语义服务发现模型

在开放的Internet环境下,多本体共存是一种必然.同时,集中式的语义服务发现机制是整个面向服务计算的瓶颈,导致系统的可扩展性差.为了支持多本体共存并提高系统的可扩展性,提出一种双层P2P语义服务发现模型.该模型以本体社区为核心,将iVCE(Internet-based virtual computing environment)的核心概念集成到P2P模型中.基于该模型,提出一种分两个阶段、3个步骤的服务发现算法.除了在本体社区内以外,算法还可以实现跨社区的服务发现.在本体社区内,算法首先根据语义相似性选定相应的注册服务器,然后再利用逻辑推理来实施精确的服务匹配.而跨社区的服务发现则按照一定的策略实施.该模型适用于多本体共存的开放环境.实验结果表明,通过合理的参数配置,模型能在查全率和服务发现响应时间之间加以折衷,并取得较好的结果;另外,模型能够在不降低服务查全率的情况下降低注册服务节点的平均负载.     

一种基于本体的语义Web服务发现模型

Web服务已经成为互联网中最为重要的一种计算资源和软件资产,Web服务的大量涌现对服务发现提出了挑战。Web服务发现的关键是Web服务的语义描述的准确性和Web服务检索引擎的检索效率。提出了一种基于本体的Web服务描述方法,采用OWL-S对Web服务进行语义描述,并提出了针对性的Web服务检索引擎。通过试验,该模型结合语义Web服务技术实现Web服务的动态查找与组合,可提高Web服务发现的查全率和查准率。     

Joint semantic similarity assessment with raw corpus and structured ontology for semantic-oriented service discovery

Semantic-oriented service matching is one of the challenges in automatic Web service discovery. Service users may search for Web services using keywords and receive the matching services in terms of their functional profiles. A number of approaches to computing the semantic similarity between words have been developed to enhance the precision of matchmaking, which can be classified into ontology-based and corpus-based approaches. The ontology-based approaches commonly use the differentiated concept information provided by a large ontology for measuring lexical similarity with word sense disambiguation. Nevertheless, most of the ontologies are domain-special and limited to lexical coverage, which have a limited applicability. On the other hand, corpus-based approaches rely on the distributional statistics of context to represent per word as a vector and measure the distance of word vectors. However, the polysemous problem may lead to a low computational accuracy. In this paper, in order to augment the semantic information content in word vectors, we propose a multiple semantic fusion (MSF) model to generate sense-specific vector per word. In this model, various semantic properties of the general-purpose ontology WordNet are integrated to fine-tune the distributed word representations learned from corpus, in terms of vector combination strategies. The retrofitted word vectors are modeled as semantic vectors for estimating semantic similarity. The MSF model-based similarity measure is validated against other similarity measures on multiple benchmark datasets. Experimental results of word similarity evaluation indicate that our computational method can obtain higher correlation coefficient with human judgment in most cases. Moreover, the proposed similarity measure is demonstrated to improve the performance of Web service matchmaking based on a single semantic resource. Accordingly, our findings provide a new method and perspective to understand and represent lexical semantics.     

对等模式下语义Web服务发布与发现技术综述

在面向服务的计算中,服务发现是关键。服务发现是在因特网范围内Web服务自动组合、应用即时构造的基础,近年来被学术和工业界广泛关注,相关技术层出不穷。针对Web服务发布发现技术当前研究成果,进行了系统的归纳分类。重点从关键字匹配和语义特征发布两个角度,对对等环境下W cb服务发布发现技术的主要研究工作进行了论述。最后归纳出对等环境下语义Wcb服务发布的一般特征,以及未来对等环境下Wcb服务发布发现的主要研究目标、研究问题和挑战。     

基于多阶段匹配的语义Web服务发现框架

随着Web服务的高速发展和广泛应用,如何在众多的Web服务中找出用户所需要的Web服务成为了一个关键的问题.在语义Web服务研究的基础上,提出了一种新的多阶段匹配的语义Web服务发现框架,将整个发现过程分为服务类别、服务功能、服务名称和服务文本语句匹配4个阶段,并在服务功能匹配阶段针对本体库中概念间的密度问题,提出了基于信息量的改进GCSM算法,在服务名称和服务文本语句匹配阶段,针对中文多义词的问题提出了基于实例搭配和基本义原的消歧策略.最后,实验证明提出的发现框架具有较好的可行性和有效性.