comFlow:一个支持Web服务动态组合的原型系统

随着电子商务的迅速发展及用户对企业服务质量和及时信息反馈的要求越来越高,企业内及企业间各个系统之间的交互对企业的发展越来越重要.结合Web服务技术和流程建模技术,设计并初步实现了支持Web服务动态组合和执行的原型系统,给出了comFlow的系统架构,并描述它的组成部分.     

A dual-layered model for web services representation and composition

Nowadays more and more companies and organizations implement their business services in the Internet due to the tremendous progress made recently in the field of Web services. It becomes possible to publish, locate and invoke applications across the Web. Thus, the ability to select efficiently and integrate at runtime services located in different sites on the Web is an important issue. In some situations, if no single Web service can satisfy the request of the user, there should be a possibility to combine existing services together in order to meet the user’s request. This paper provides a dual-layered model for web services, where the first model layer captures the high-level functional specifications (namely goals, achievement contexts, and external behaviours), and the second model layer captures the low-level functional specifications (namely interfaces). This model allows the service composition process to be performed on both high-level and low-level specifications. We also introduce the composition operators (both high-level and low-level) to allow composition of virtual services.     

Semantic-based automatic service composition with functional and non-functional requirements in design time: A genetic algorithm approach

ContextIn recent years, the composition of ready-made and loosely coupled services into desired systems is a common industrial approach and a widely followed research topic in academia. In the field, the current research trend is to automate this composition; however, each of the existing efforts automates only a component of the entire problem. Therefore, a real automation process that addresses all composition concerns is lacking.ObjectiveThe objective is to first identify the present composition concerns and subsequently to devise a compositional approach that covers all concerns. Ultimately, we conduct a number of experiments to investigate the proposed approach.MethodWe identify the current composition concerns by surveying and briefly describing the existing approaches. To include all of the identified concerns, the solution space that must be searched is highly dimensioned. Thus, we adopt a genetic algorithm (GA) due to its ability to solve problems with such characteristics. Proposed GA-based approach is designed with four unusual independent fitness functions. Additionally, experiments are carried out and discussions are presented for verification of the design, including the necessity for and correctness of the independence and priority of the four fitness functions.ResultsThe case studies demonstrate that our approach can automatically generate the required composite services and considers all identified concerns simultaneously. The results confirm the need for the independence of the fitness function and also identify a more efficient priority for these functions.ConclusionsIn this study, we present an all-inclusive automatic composer that does not require human intervention and effort during the composition process and is designed for users who must address multiple composition concerns simultaneously, including requirements for overall functionality, internally workable dataflow, and non-functional transaction and quality-of-service considerations. Such multiple and complex composition requirements cannot be satisfied by any of the previous single-concern composition approaches.     

信息提供类Web服务基于查询重写的自动组合方法

现有对Web服务自动组合的研究很少考虑信息提供类服务不同于一般服务的特点.文中提出一个简单,但具有明确语义的信息提供类服务功能模型,表达了该类服务不改变世界状态,有些输入输出参数不具有语义类型的特点;然后提出并实现了一个相应的自动组合方法.该方法以数据集成领域中一种查询重写算法MiniCon为基础,充分利用了前述特点,支持最基本的语义推理,能自动生成可直接运行的BPEL脚本.其性能特点与传统的基于搜索过程的方法具有互补性.在一类典型问题上进行的性能测试表明该方法具有相当强的实用价值.     

关于Web服务组合的有效Web服务发现机制

随着Web Services的广泛流行,怎样发现适当Web Services来支持Web Services的组合已经成为一种挑战.由于传统的关键字搜索具有太低的记忆性和精确性,因此这种方法是很低效的.基于Web Services的描述信息,介绍了一种有效的Web Services发现机制.此服务发现方法是简单可用的,通过引入语义变得十分高效,因此该机制成功的在服务组合模型上得到了实现.     

Semantic web service composition testbed

A huge amount of web services are deployed on the Web, nowadays. These services can be used to fulfill online requests. Requests are getting more and more complicated over time. So, there exists a lot of frequent request that cannot be fulfilled using just one web service. For using web services, composing individual services to create the added-value composite web service to fulfill the user request is necessary in most cases. Web services can be composed manually but it is a too tedious and time consuming task. The ability of automatic web service composition to create a new composite web service is one of the key enabling features for the future for the semantic web. There are some successful methods for automatic web service composition, but the lack of standard, open, and lightweight test environment makes the comparison and evaluation of these composition methods impossible. In this paper we propose an architecture for a light weight and scalable testbed to execute, test and evaluate automatic web service composition algorithms. The architecture provides mandatory components for implementing and evaluation of automatic web service composition algorithms. Also, this architecture provides some extension mechanisms to extend its default functionalities. We have also given reference implementations for web service matchmaking and composition. Also, some scenarios for testing and evaluating the testbed are given. We have found that the performance of the composition method will dramatically decrease as the number of web services increases.     

基于服务提供方与请求方的语义Web服务选取的研究*

随着Web服务的增多,如何从一批相似的服务中选出最佳的服务已成为研究的热点,当用服务质量或信誉度来作为服务的选取依据时,都只是从服务提供方的角度出发,没有考虑到服务请求方的主要作用与个性。论文充分考虑请求方与提供方的情况,结合了服务提供方的信誉度与服务请求方的满意度,以请求方的满意度为主,参考提供方的信誉度,提出了一个服务发现与选取的参考模型WSDM—CS,并结合本体深入讨论了信誉度与满意度的实现算法,并应用到语义Web服务中, 以提高在语义Web服务选择中的准确性和可靠性。     

An architectural design for effective information retrieval in semantic web

The current web IR system retrieves relevant information only based on the keywords which is inadequate for that vast amount of data. It provides limited capabilities to capture the concepts of the user needs and the relation between the keywords. These limitations lead to the idea of the user conceptual search which includes concepts and meanings. This study deals with the Semantic Based Information Retrieval System for a semantic web search and presented with an improved algorithm to retrieve the information in a more efficient way.This architecture takes as input a list of plain keywords provided by the user and the query is converted into semantic query. This conversion is carried out with the help of the domain concepts of the pre-existing domain ontologies and a third party thesaurus and discover semantic relationship between them in runtime. The relevant information for the semantic query is retrieved and ranked according to the relevancy with the help of an improved algorithm. The performance analysis shows that the proposed system can improve the accuracy and effectiveness for retrieving relevant web documents compared to the existing systems.     

Extensible soft semantic web services agent

Web services technology is critical for the success of business integration and other application fields such as bioinformatics. However, there are two challenges facing the practicality of Web services: (a) efficient location of the Web service registries that contain the requested Web services and (b) efficient retrieval of the requested services from these registries with high quality of service (QoS). The main reason for this problem is that current Web services technology is not semantic-oriented. Several proposals have been made to add semantics to Web services to facilitate discovery and composition of relevant Web services. Such proposals are being referred to as semantic Web services (SWS). However, most of these proposals do not address the second problem of retrieval of web services with high QoS. In this paper, we propose a framework called soft semantic Web services agent (soft SWS agent) for providing high QoS Semantic Web services using soft computing methodology. Since different application domains have different requirement for QoS, it is impractical to use classical mathematical modeling methods to evaluate the QoS of semantic Web services. We use fuzzy neural networks with Genetic Algorithms (GA) as our study case. Simulation results show that the soft computing methodology is practicable to handle fuzzy and uncertain QoS metrics effectively.     

动态Web服务合成中的服务选择算法研究

为了提高服务合成效率并更好的适应动态变化的应用环境,提出了基于流程修改的服务合成方案,使得复合服务的执行与服务发现过程并行化。提出了基于QoS属性的服务选择算法,该算法能够实现服务执行时选择服务,在考虑综合QoS信息及时间因素的基础上,通过不断更新用户需求来进行服务选择,提高了服务合成效率。实验结果表明,该选择算法可以获得满足用户需求且最优的服务,很好的保证了服务的可靠执行。