Semantic based aspect-oriented programming for context-aware Web service composition

An aspect-oriented programming (AOP) based approach is proposed to perform context-aware service composition on the fly. It realises context-aware composition by semantically weaving context into Web service composition. The context weaver algorithm is implemented and illustrated. The proposed semantic weaving allows Web services to be composed as the context changes.     

XrML-RBLicensing approach adapted to the BPEL process of composite web services

Web service orchestration represents an open and standards-based approach for connecting web services together leading to higher level of business processes. Business Process Execution Language (BPEL) engines are designed to handle this orchestration. However, web service compositions into BPEL suffer from several non-functional requirements such as security. To address this problem, we propose in this paper a novel approach that is based on a harmony between the licensing concept offered by eXtensible rights Markup Language (XrML), aspect-oriented programming (AOP), and web service compositions in BPEL. Our proposed approach, based on XrML, offers the ability to associate security licenses with activities offered by the composite web services. It allows to automatically generate BPEL aspects depending on the developed licenses, to separate between crosscutting concerns of the composed web services, and provides an easy way to include and update the non-functional requirements (e.g., security) into a BPEL process. It offers also the ability to validate the licenses, at runtime and without affecting the business logic of this model. To evaluate our approach, we have developed an inventory control system (ICS) sample that is composed of several web services. Case study and performance analysis are presented to demonstrate its feasibility as well.     

Context-based matching for Web service composition

In this paper, we propose a novel matching framework for Web service composition. The framework combines the concepts of Web service, context, and ontology. We adopt a broad definition of context for Web services, encompassing all information needed for enabling interactions between clients and providers. Context-based matching for Web services requires dealing with three major research thrusts: context categorization, modeling, and matching. We first propose an ontology-based categorization of contextual information in Web service environments. We then define a two-level mechanism for modeling Web service contexts. In the first level, service providers create context specifications using category-specific Web service languages and standards. In the second level, context specifications are enveloped by policies (called context policies) using WS-Policy standard. Finally, we present a peer-to-peer architecture for matching context policies. The architecture relies on a context matching engine, context policy assistants, and context community services. Community services implement rule-based techniques for comparing context policies. Recommended by: Zakaria Maamar     

AO4BPEL: An Aspect-oriented Extension to BPEL

Process-oriented composition languages such as BPEL allow Web Services to be composed into more sophisticated services using a workflow process. However, such languages exhibit some limitations with respect to modularity and flexibility. They do not provide means for a well-modularized specification of crosscutting concerns such as logging, persistence, auditing, and security. They also do not support the dynamic adaptation of composition at runtime. In this paper, we advocate an aspect-oriented approach to Web Service composition and present the design and implementation of AO4BPEL, an aspect-oriented extension to BPEL. We illustrate through examples how AO4BPEL makes the composition specification more modular and the composition itself more flexible and adaptable.     

Service-Oriented Computing: Bringing Business Systems to the Web

The notion of "service" has spurred major evolutions for both information systems and the Web. A software application is no longer considered a monolithic component; it can be divided into services that are smaller components defined by their function and accessible through well-defined interfaces and protocols. As a result, IT actors are using service-oriented architectures (SOAs) to remodel the information systems of many companies while the Web is increasingly becoming a programmable place. In both domains, developers build composite client applications to consume these services. Even boundaries between enterprise services and Internet services are vanishing. Some companies, such as Strikelron provide enterprise services that were previously always hosted internally - like customer relationship management solutions. As a consequence, companies now have the technologies required to bring their business online. With Web services, private business processes can be exposed to partners through public composite Web applications. When new projects emerge, companies need guidance to properly handle such work. In this context, we aim to provide companies solutions - through a methodology, an architecture, and technical choices - that will help them solve generic problems such as security and application conception     

一种规则驱动的网络服务组装机制

提出了一种规则驱动的服务组装方法,实现了一个基于软件Agent的框架,在运行时刻监控和管理组装流程的执行．该方法给出一个算法将流程规约转化为等价的规则集合以用于指导Agent的行为,并允许用户通过定义一组可插拔(pluggable)的自适应策略,方便地扩展流程对变化的适应能力．框架实现基于反射式中间件平台PKUAS,该平台为网络服务和软件Agent提供运行支持,并基于其反射机制为Agent提供运行时刻的环境信息．     

Using Policies to Manage Composite Web Services

When no single Web service can fulfil a user's request, providers often turn to composite Web services. However, developing a composite Web service is not simple and deploying the composition specification at runtime consists of several processes. Developers and deployers of composite Web services can use policies in various scenarios, from the announcement of Web services to the compatibility between Web services and composite Web services. Mapping guidelines for a Web service's behavior to policies can ensure an individual Web service's smooth engagement into a composite Web service     

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。     

A simulation-based approach for dynamic process management at web service platforms

Web services technology is being adopted as a viable deployment approach for future distributed software systems that enable business-to-business and business-to-consumer interactions across the open and dynamic internet environment. Recent research is focused on developing support technologies for web service discovery, on-demand service composition, and robust execution to facilitate web services based deployment of business processes. Developing techniques to cope with the volatile and open nature of the web during execution of composite services at the service platform is essential for delivering reliable and acceptable performance in this new process delivery framework. In this paper, we propose a simulation-based framework to guide scheduling of composite service execution. Online simulation of the dynamics of the open environment is used for scheduling service requests at the service platform. Comparison of the look-ahead simulation for different scheduling policies with the current execution state provides guidelines for service execution in order to cope with system volatility. We have implemented a prototype of the proposed framework and illustrate the feasibility of our approach with experimental studies.     

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.     

Autonomic resource provisioning for software business processes

Software development nowadays involves several levels of abstraction: starting from the programming of single objects, to their combination into components, to their publication as services and the overall architecture linking elements at each level. As a result, software engineering is dealing with a wider range of artifacts and concepts (i.e., in the context of this paper: services and business processes) than ever before. In this paper we explore the importance of having an adequate engine for executing business processes written as compositions of Web services. The paper shows that, independently of the composition language used, the overall scalability of the system is determined by how the run-time engine treats the process execution. This is particularly relevant at the service level because publishing a process through a Web service interface makes it accessible to an unpredictable and potentially very large number of clients. As a consequence, the process developer is confronted with the difficult question of resource provisioning. Determining the optimal configuration of the distributed engine that runs the process becomes sensitive both to the actual number of clients and to the kinds of processes to be executed. The main contribution of the paper is to show how resource provisioning for software business processes can be solved using autonomic computing techniques. The engine separates execution in two stages (navigation and dispatching) and uses a controller to allocate the node of a cluster of computers to each one of those stages as the workload changes. The controller can be configured with different policies that define how to reconfigure the system. To prove the feasibility of the concept, we have implemented the autonomic controller and evaluated its performance with an extensive set of experiments.     

Semantic specification and evaluation of bids in web-based markets

In recent years, electronic markets have gained much attention as institutions to allocate goods and services efficiently between buyers and sellers. By leveraging the Web as a global communication medium, electronic markets provide a platform that allows participants throughout the world to spontaneously exchange products in a flexible manner. However, ensuring interoperability and mutual understanding in such a highly dynamic and heterogenous environment can easily become very tricky, particularly if the services and goods involved are complex and described by multiple attributes. In this paper, we present a comprehensive ontology framework that allows the specification of bids for Web-based markets. By expressing utility function policies with a logic-based and standardized formalism, the framework enables a compact bid representation particularly for highly configurable goods and services while ensuring a high degree of interoperability. To facilitate matchmaking of offers and requests in the market, a method for evaluating bids based on logical reasoning is presented. In addition, as proof of concept, we show how the framework can be applied in a Web service selection scenario.     

Toward Behavioral Web Services Using Policies

Making Web services context-aware is a challenge. This is like making Web service expose appropriate behaviors in response to changes detected in the environment. Context awareness requires a review and extension of the current execution model of Web services. This paper discusses the seamless combination of context and policy to manage behaviors that Web services expose during composition and in response to changes in the environment. For this purpose, a four-layer approach is devised. These layers are denoted by policy, user, Web service, and resource. In this approach, behavior management and binding are subject to executing policies of types permission, obligation, restriction, and dispensation. A prototype that illustrates how context and policy are woven into Web services composition scenarios is presented as well.      

基于软件代理和上下文的Web服务合成方法

Web服务的诸多特性使得它非常适合于商务应用集成，工业界和学术界都希望能够通过合成多个Web服务从而获得增值的新服务。介绍两个概念以减少Web服务合成的复杂性：软件代理和上下文；并论述了在合成期间，软件代理之间进行会话以同意Web服务参与到合成中。     

A layered architecture for flexible Web service invocation

Web service composition is emerging as an interesting approach to integrate business applications and create intra‐organizational business processes. Single Web services are combined to create a complex Web service that will realize the process business logic. Once the process is created, it is executed by an orchestration engine that invokes individual Web services in the correct order. However, Web services composing the workflow sometimes become unavailable during the run‐time phase, blocking process execution. This paper describes an architecture that allows the flexible orchestration of business processes. With this approach, Web services composing the process can be automatically substituted with other compatible Web services during process execution. A methodology is defined to evaluate Web service compatibility based on interface matching, in order to select substitutable Web services. Copyright © 2005 John Wiley & Sons, Ltd.     

Web服务设计中的访问控制验证*

提出了一种新颖的方法,用于在设计阶段确定Web服务设计是否能根据其访问控制策略及凭证发布策略进行实施。将Web服务和Web服务设计均模拟为演进系统,并用有向图表示Web服务的凭证发布策略。证明了Web服务设计中所有可能的会话,其实都可以通过将请求者Web服务的凭证发布策略与被请求者Web服务的访问控制策略相匹配而实现。利用了一个资源发布图来完成这种证明。     

Improving device-aware Web services and their mobile clients through an aspect-oriented,model-driven approach

ContextMobile devices have become an essential element in our daily lives, even for connecting to the Internet. Consequently, Web services have become extremely important when offering services through the Internet. However, current Web services are very inflexible as regards their invocation from different types of device, especially if we consider the need for them to be adaptable when being invoked from mobile devices.ObjectiveIn this paper, we provide an approach for the creation of flexible Web services which can be invoked transparently from different device types and which return subsequent responses, as well as providing the client’s adaptation as a result of the particular device characteristics and end-user preferences in a completely decoupled way.MethodAspect-Oriented Programming and model-driven development have been used to reduce both the impact of service and client code adaptation for multiple devices as well as to facilitate the developer’s task.ResultsA model-driven methodology can be followed from system models to code, providing the Web service developer with the option of marking which services should be adapted to mobile devices in the UML models, and obtaining the decoupled adaptation code automatically from the models.ConclusionWe can conclude that the approach presented in this paper provides us with the possibility of following the development of mobile-aware Web services in an integrated platform, benefiting from the use of aspect-oriented techniques not only for maintaining device-related code completely decoupled from the main functionality one, but also allowing a modularized non-intrusive adaptation of mobile clients to the specific device characteristics as well as to final user preferences.     

Adaptive Service Composition in Flexible Processes

In advanced service oriented systems, complex applications, described as abstract business processes, can be executed by invoking a number of available Web services. End users can specify different preferences and constraints and service selection can be performed dynamically identifying the best set of services available at runtime. In this paper, we introduce a new modeling approach to the Web service selection problem that is particularly effective for large processes and when QoS constraints are severe. In the model, the Web service selection problem is formalized as a mixed integer linear programming problem, loops peeling is adopted in the optimization, and constraints posed by stateful Web services are considered. Moreover, negotiation techniques are exploited to identify a feasible solution of the problem, if one does not exist. Experimental results compare our method with other solutions proposed in the literature and demonstrate the effectiveness of our approach toward the identification of an optimal solution to the QoS constrained Web service selection problem