CASD: Management of a context-aware service directory

Traditional web service discovery is strongly related to the use of service directories. Especially in the case of mobile web services, where both service requestors and providers are mobile, the dynamics impose the need for directory-based discovery. Context plays an eminent role with mobility, as a filtering mechanism that enhances service discovery through the selection of the most appropriate service. However, current service directory specifications do not focus on mobility of services or context-awareness. In this paper, we propose CASD, a context-aware service directory, envisioned as a context-based index for services on top of any traditional service directory, and design algorithms for construction, search, update and merge of such directories. Furthermore, we describe the architecture of our system for context-aware service discovery, we present a prototype implementation and discuss the experimental results as well as the overall evaluation. The contribution of this work is the proposal for a novel, enhanced representation model for a context-aware service directory.     

基于策略的可控服务发现与动态路由模型

如何改进现有服务发现模型使之适应动态可变的服务运行环境并选择最符合用户需求的Web服务正在引起研究领域关注.提出了一种基于策略的可控服务发现与动态路由模型(P-WSDRM).该模型支持抽象服务、服务实例和服务发现者的属性定义,支持携带属性描述信息的服务发布与发现,引入了策略判定机制,支持服务发现者基于已定义的策略进行服务发现和实例路由.目前已经于Linux平台和目录服务实现了该模型的一个原型系统.     

Semantic web services publication and OCT-based discovery in structured P2P network

Semantic web services (SWS) technology is developed to overcome the shortcomings of traditional standards, such as WSDL and UDDI, and enable maximal automation in all aspects of web service. But great improvement of capability in SWS-based service discovery is still desired. To address this issue, we present a distributed and semantic-matching-based approach for SWS publication and discovery by leveraging structured P2P technology. In this paper, first, we present our service matching rule which focuses on the inputs and outputs of SWS. Then, to realize this rule in open distributed environment and achieve the optimal match between a query and its qualified services, we propose not only a concept of ordered-concept-tree (OCT) to semantically sort the relevant concepts for service matching, but also a method to publish ontologies on structured P2P network to freely share and make full use of the concepts defined in different ontologies for OCT construction. Finally, we present a method for SWS publication on P2P network and an algorithm for service discovery. We also conduct experiments to evaluate our approach and the experimental results demonstrate its scalability, effectiveness, and callback capability to discover semantic web services.     

Service discovery in mobile ad hoc networks: A field theoretic approach

Service discovery in mobile ad hoc networks is challenging because of the absence of any central intelligence in the network. Traditional solutions as used in the Internet are hence not well suited for mobile ad hoc networks. In this paper, we present a novel decentralized service discovery mechanism for ad hoc networks. The basic idea is to distribute information about available services to the network neighborhood. We achieve this by using the analogy of an electrostatic field: A service is modelled by a (positive) point charge, and service request packets are seen as (negative) test charges which are attracted by the service instances. In our approach, we map the physical model to a mobile ad hoc network in a way where each network element calculates a potential value and routes service requests towards the neighbor with the highest potential, hence towards a service instance. Our approach allows for differentiation of service instances based on their capacity. We define the required protocols and methods which we implemented in a network simulator. Using extensive simulations, we evaluate the performance and robustness of the mechanisms. The results indicate good performance and convergence even in highly mobile environments. We believe that this technique can and should be further exploited, e.g., as a routing protocol in mobile ad hoc networks.     

Kontextbasierte Kooperation für mobile Geschäftsanwendungen

Realistic requirements of mobile business applications often exceed the capabilities of their respective local environments. In order to overcome such restrictions of specific mobile devices, services, and resources, this contribution introduces the concept of context-based cooperation. It is based on mobile processes which enable applications to cross boundaries of individual systems and thereby allow combining both mobile and stationary resources in order to realize highly dynamic individual applications. This contribution presents an approach for realizing context-based cooperation built upon on a respective context management infrastructure and execution environment. It also identifies specific requirements and proposes related enhancements for mobile business applications.     

基于策略的Web服务非功能属性匹配

Web服务的非功能属性匹配对增强Web服务发现的准确性，保证Web服务调用质量具有重要作用。目前Web服务的非功能属性匹配研究一般局限于某一具体的非功能属性，缺少支持各非功能属性的统一匹配方法。该文提出了一种基于策略的Web服务非功能属性的匹配方法，把Web服务非功能属性作为服务双方的策略，利用策略匹配来实现非功能属性的匹配。采用WSPL作为策略描述语言，并提出了层次化策略的概念，利用不同的发布方式对不同层次的策略进行发布，服务发现的过程与不同层次的策略匹配结合在一起。该方法支持各种非功能属性的匹配，并可以容易地和Web服务的功能性匹配方法结合到一起，形成完整的Web服务发现匹配系统。     

基于服务上下文的Web服务发现机制

服务发现成为Web服务组合研究的重点,为解决服务组合过程中服务发现方法存在动态适应能力不足,提出了一种基于服务上下文的Web服务发现机制.该机制将一种服务本体描述语言OWL-S和一种基于服务上下文的服务发现算法相结合,利用语义描述服务的信息,同时定义了服务上下文信息并进行服务上下文匹配来发现所需服务.实验结果表明,基于服务上下文的Web服务发现机制能够提高服务发现的准确性,具有较好地动态适应性.     

一种基于双层环网络的Web服务发现方法

结合One-hop和Chord路由机制,考虑实际网络中节点能力的差异,构造一种双层环路由结构,设计相应的区间查询定位和消息广播算法,提出一种基于本体聚类的双层环P2P网络的Web服务发现方法,实现了服务注册节点分类和查询请求迅速准确的定位。模拟实验结果表明,该方法具有较高搜索效率和较短的响应时间,能够显著地提高查询性能。     

MobiEureka: an approach for enhancing the discovery of mobile web services

While several service discovery protocols and standards have been proposed for supporting service discovery from mobile devices, this remains a challenging problem. In many cases, mobile clients may discover services which they consider relevant but soon realize that such services are not completely usable on their mobile devices due to compatibility and interoperability issues. Without integrating device capabilities into the discovery process, or a device-aware mobile service discovery, it becomes extremely difficult to determine whether discovered services may or may not function properly within the device’s constraints. This paper introduces a solution known as MobiEureka, a mobile device-aware system for enhancing the discovery of mobile web services from mobile devices. Experimental validation, results, and analysis of the introduced ideas are discussed.     

基于P2P的Web服务发现机制研究

在P2P系统中融入Web服务的相关技术,将传统的P2P系统转变为一种面向服务的架构是分布式计算发展的方向,而Web服务的自动发现是面向服务的架构要解决的关键问题之一.提出了一种基于P2P技术和语义Web的服务发现机制,将P2P系统作为服务的提供者整体接入Web服务,通过P2P网络实现服务描述信息的自动交换,并采用分段搜索机制处理用户查询,从而提高了用户查询的效率和准确性.