Minimum-cost delegation in service composition

The paradigm of automated service composition through the integration of existing services promises a fast and efficient development of new services in cooperative service (e.g., business) environments. Although the “why” part of this paradigm is well understood, many key pieces are missing to utilize the available opportunities. Recently “service communities” where service providers with similar interests can register their services are proposed toward realizing this goal. In these communities, requests for services posed by users can be processed by delegating them to existing services, and orchestrating their executions. We use a service framework similar to the “Roman” model departing from it particularly assuming service requirements are specified in a sequence form. We also extend the framework to integrate activity processing costs into the delegation computation and to have services with bounded storage as opposed to finite storage. We investigate the problem of efficient processing of service requests in service communities and develop polynomial time delegation techniques guaranteeing optimality.     

Dynamic web service composition based on OWL-S

Composing existing web services for enterprise applications may enable higher level of reuse. However the composition processes are mostly static and lack of support for runtime redesign. In this paper, we describe our approach to the extension of the OWL-S ontology framework for dynamic web service composition. We raise the level of abstraction and propose an abstract service layer so that web services can be com- posed at the abstract service level instead of the concrete level. Each abstract service is attached with an instance pool including all instances of the abstract service to facilitate fail-over and dynamic compositions.     

Service composition for generic service graphs

Service composition is a promising approach to multimedia service provisioning, due to its ability to dynamically produce new multimedia content, and to customize the content for individual client devices. Previous research work has addressed various aspects of service composition such as composibility, QoS-awareness, and load balancing. However, most of the work has focused on applications where data flow from a single source is processed by intermediate services and then delivered to a single destination. In this paper, we address the service composition problem for multimedia services that can be modeled as directed acyclic graphs (DAGs). We formally define the problem and prove its NP hardness. We also design a heuristic algorithm to solve the problem. Our simulation results show that the algorithm is effective at finding low-cost composition solutions, and can trade off computation overhead for better results. When compared with a hop-by-hop approach for service composition, our algorithm can find composition solutions that aress 10% smaller in cost, even when the hop-by-hop approach uses exhaustive searches.     

Self-scaling cooperative discovery of service compositions in unstructured P2P networks

We propose an efficient technique for improving the performance of automatic and cooperative compositions in unstructured Peer-to-Peer networks during service discovery. The technique exploits a probabilistic forwarding algorithm that uses different sources of knowledge, such as network density and service grouping, to reduce the amount of messages exchanged in the network. The technique, analysed in several network configurations by using a simulator to observe resolution time, recall and message overhead, presents good performance especially in dense and large-scale service networks.     

一种高效的车载自组网服务发现策略

人们对车载网络中服务的需求越来越多,而现有的有线网络和一般AdHoc网络的服务发现协议并不适用于车载网络。因此,在车载信息传播协议的基础上,利用服务强度的概念,提出了一种在城区车载网络中能高效选择最优下一跳节点的服务发现策略,成功实现低数据包开销下的车载网络服务发现。通过仿真比较,验证了其较好的可扩展性。     

Time-aware prefetching for on-demand video services in a residential service gateway

With the recent advances in network technology, the number of high-speed networked homes increases rapidly and the enhanced services such as on-demand video services become feasible in terms of market maturity. Another trend is that storage systems become network-accessible. One of the leading network-attached storage systems is the Fiber Channel Arbitrated Loop (FC-AL). As a residential service gateway, the FC-AL-based servers can stably provide high quality video (e.g., DVD quality MPEG-2 stream) with thousands of clients between external service providers and local clients. In addition, in densely populated areas such as New York City, they can be much more cost efficient. Using our end-to-end simulation experiments to combine all the components, we have observed that FC-AL-based streaming servers perform better than SCSI-based systems, but there is still room for performance improvement. We are motivated by the fact that, unlike in SCSI-based systems, all the disks in FC-AL-based severs utilize only a small portion of their caches to a similar degree due to FC-AL fairness arbitration algorithm. Thus, we propose an effective prefetching scheme to improve the performance by further utilizing the disk cache. We show how the proposed scheme can determine the maximum number of prefetched blocks depending on the disk block and cache size. It is also shown how to find the optimal number of blocks transmitted to the FC-AL from the disk cache per FC-AL arbitration. In addition, we describe the cache replacement policy to take full advantage of the sequential access pattern of video files, and explain how to support multiple loops. By analysis and simulation experiments, we show that our prefetching scheme is not able to only increase the total number of concurrent streams significantly by reducing the disk seek time, but it can also further utilize the FC-AL by reducing the overhead of arbitration.

Computing compatibility in dynamic service composition

Dynamically composing services requires mechanisms to ensure component services compatible with each other both at all of the syntax, semantic and behavioral level. This paper focuses on the issue of behavioral compatibility in a service composition. It adopts the π-calculus to model service behaviors and interactions in a formal way. Based on the formalization, it proposes a method to automatically check the behavioral compatibility in a qualitative way. Furthermore, it presents an algorithm to compute the compatibility degree in a quantitative way. The algorithm is implemented in a prototype and its performance analysis is also carried out to show that it can help composing services on the fly and ensure the services compatible with each other to provide functions with newly-added values.

Managing service level agreements in Premium IP networks: a business-oriented approach

This paper presents a market-enabling framework where users, content providers and network operators can interact in the seamless, transparent sale and delivery of a wide range of services. The framework allows for dynamic creation, configuration and delivery of services with quality assurance, via automated management of Service Level Agreements (SLAs). We propose an approach relying on a systemic treatment of business, service and network layer issues, which translates into a layered architecture where components belonging to different levels interact on the basis of a mediation paradigm. We use mediation as a generic term for a combination of negotiation, brokerage and state notification, jointly concurring to the realization of the entire life-cycle of a service.     

Dynamic SLAs management in service oriented environments

The increasing adoption of service oriented architectures across different administrative domains, forces service providers to use effective mechanisms and strategies of resource management in order for them to be able to guarantee the quality levels their customers demands during service provisioning. Service level agreements (SLA) are the most common mechanism used to establish agreements on the quality of a service (QoS) between a service provider and a service consumer. The WS-Agreement specification, developed by the Open Grid Forum, is a Web Service protocol to establish agreements on the QoS level to be guaranteed in the provision of a service. The committed agreement cannot be modified during service provision and is effective until all activities pertaining to it are finished or until one of the signing party decides to terminate it. In B2B scenarios where several service providers are involved in the composition of a service, and each of them plays both the parts of provider and customer, several one-to-one SLAs need to be signed. In such a rigid context the global QoS of the final service can be strongly affected by any violation on each single SLA. In order to prevent such violations, SLAs need to adapt to any possible needs that might come up during service provision. In this work we focus on the WS-Agreement specification and propose to enhance the flexibility of its approach. We integrate new functionality to the protocol that enable the parties of a WS-Agreement to re-negotiate and modify its terms during the service provision, and show how a typical scenario of service composition can benefit from our proposal.     

S-Club: an overlay-based efficient service discovery mechanism in CROWN Grid

Information service plays a key role in grid system, handles resource discovery and management process. Employing existing information service architectures suffers from poor scalability, long search response time, and large traffic overhead. In this paper, we propose a service club mechanism, called S-Club, for efficient service discovery. In S-Club, an overlay based on existing Grid Information Service (GIS) mesh network of CROWN is built, so that GISs are organized as service clubs. Each club serves for a certain type of service while each GIS may join one or more clubs. S-Club is adopted in our CROWN Grid and the performance of S-Club is evaluated by comprehensive simulations. The results show that S-Club scheme significantly improves search performance and outperforms existing approaches. Chunming Hu is a research staff in the Institute of Advanced Computing Technology at the School of Computer Science and Engineering, Beihang University, Beijing, China. He received his B.E. and M.E. in Department of Computer Science and Engineering in Beihang University. He received the Ph.D. degree in School of Computer Science and Engineering of Beihang University, Beijing, China, 2005. His research interests include peer-to-peer and grid computing; distributed systems and software architectures. Yanmin Zhu is a Ph.D. candidate in the Department of Computer Science, Hong Kong University of Science and Technology. He received his B.S. degree in computer science from Xi’an Jiaotong University, Xi’an, China, in 2002. His research interests include grid computing, peer-to-peer networking, pervasive computing and sensor networks. He is a member of the IEEE and the IEEE Computer Society. Jinpeng Huai is a Professor and Vice President of Beihang University. He serves on the Steering Committee for Advanced Computing Technology Subject, the National High-Tech Program (863) as Chief Scientist. He is a member of the Consulting Committee of the Central Government’s Information Office, and Chairman of the Expert Committee in both the National e-Government Engineering Taskforce and the National e-Government Standard office. Dr. Huai and his colleagues are leading the key projects in e-Science of the National Science Foundation of China (NSFC) and Sino-UK. He has authored over 100 papers. His research interests include middleware, peer-to-peer (P2P), grid computing, trustworthiness and security. Yunhao Liu received his B.S. degree in Automation Department from Tsinghua University, China, in 1995, and an M.A. degree in Beijing Foreign Studies University, China, in 1997, and an M.S. and a Ph.D. degree in computer science and engineering at Michigan State University in 2003 and 2004, respectively. He is now an assistant professor in the Department of Computer Science and Engineering at Hong Kong University of Science and Technology. His research interests include peer-to-peer computing, pervasive computing, distributed systems, network security, grid computing, and high-speed networking. He is a senior member of the IEEE Computer Society. Lionel M. Ni is chair professor and head of the Computer Science and Engineering Department at Hong Kong University of Science and Technology. Lionel M. Ni received the Ph.D. degree in electrical and computer engineering from Purdue University, West Lafayette, Indiana, in 1980. He was a professor of computer science and engineering at Michigan State University from 1981 to 2003, where he received the Distinguished Faculty Award in 1994. His research interests include parallel architectures, distributed systems, high-speed networks, and pervasive computing. A fellow of the IEEE and the IEEE Computer Society, he has chaired many professional conferences and has received a number of awards for authoring outstanding papers.     

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.     

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.     

Conformance analysis in networks with service level agreements

To achieve some level of Quality of Service (QoS) assurance, a network usually has Service Level Agreements (SLAs) with its users and neighboring domains, which describe the QoS level that the service provider is committed to provide, and the specification of traffic that users or neighboring domains are allowed to send. An interesting and important question arises as to whether a flow is still conformant to its original traffic specification after crossing the network since it may interact with other flows within the network. In this paper, we study analytically the extent to which a flow and an aggregate of flows become non-conformant through an analysis of the stochastic burstiness increase of flows after crossing a per-flow scheduling network and an aggregate scheduling network . The stochastic behavior of a server in aggregate scheduling networks is also studied to determine the conformance deterioration of individual flows, which provides the theoretical conformance deterioration bound and provides useful results for conformance analysis in an aggregate scheduling network with general topology. Our theoretical results are verified by extensive simulations.     

Trust-based service composition in multi-domain environments under time constraint

Trust plays a pivotal role in decision support for service-oriented computing networks. Recent advances in service evaluation and selection have provided some preliminary findings on the construction of composite services. However,the great expense of interdomain validations,the dynamic execution time and the subjective requirement for global execution time remain serious obstacles to the trust-based service composition.To solve these issues,this paper proposes a novel service-composition approach,modeling the trust-based service composition as the multi-domain scheduling and assignment problem using the minimum service resources within a certain time constraint. In our approach,each service is designed as an exclusive resource during its execution.By analyzing the required interdomain communications,the number of available services and the aggregated trust value in each domain,the optimal domain can be obtained at each step of service selection. Meanwhile,loop parallelization and predecessor reselection are adopted when the task cannot be completed on schedule. Finally,to raise higher trust value of the composite result,the redundant service resources of the initial composition are further optimized. The experimental results illustrate that the proposed trust-based service-composition approach outperforms traditional ones in both effectiveness and scalability under various time constraints.     

Dynamic control of service rates in queuing networks

A method for dynamic control of service rates in closed exponential queuing networks is proposed. The performance of queuing networks with the service-rate control is analyzed, and the main steady-state network characteristics are computed using an analytic approximation. A simple example of a queuing network with controlled service rates is considered as an illustration. The efficiency of the service-rate control is confirmed by Monte Carlo simulations, which, as a by-product, also show acceptable accuracy of our analytical approximations.     

Time-bounded distributed QoS-aware service configuration in heterogeneous cooperative environments

The scarcity and diversity of resources among the devices of heterogeneous computing environments may affect their ability to execute services within the users’ requested Quality of Service levels, particularly in open real-time environments where the characteristics of the computational load cannot always be predicted in advance but, nevertheless, response to events still has to be provided within precise timing constraints in order to guarantee a desired level of performance.     

基于LG-MMAS算法的制造云服务优化组合研究

制造云服务组合是一种提高云制造资源利用率,实现制造资源增值的新技术,对云制造产业的快速发展具有重要的支撑作用。随着云制造技术的日益成熟,网络上出现了大量具有相同制造功能和不同服务质量的制造云服务,如何通过这些制造云服务构建出既能满足用户制造需求,又具有最优服务质量的组合服务是云制造领域面临的难题。针对这一问题,将协作学习、变异和精英保留机制引入最大最小蚁群算法,构造了具有学习和变异能力的最大最小蚁群算法,并使用该算法求解服务质量感知的制造云服务优化组合问题。仿真实验结果验证了算法的有效性。     

普及计算中基于接口语义描述的动态服务组合方法

在普及计算环境中缺乏把已经存在的简单的服务灵活地动态地组合出更加复杂的服务的方法．提出了一种在此环境下的基于接口语义匹配的动态服务组合方法,给出了基于语义的基本服务的描述规范、组合服务的描述规范、组合服务的实例生成算法和控制执行的动态服务组合的系统框架并通过实例实现,验证了该框架的可行性．根据当前环境中已有的服务组合出更加复杂的服务,该算法对有效地利用系统的资源、降低服务设计和实现的复杂性具有非常重要的意义．