基于不确定服务质量感知的云服务组合方法

针对不确定服务质量（QoS）感知的云服务组合优化问题的求解,提出一种不定长时间序列（ULST）模型和锦标赛策略的改进遗传算法（T-GA）。首先,基于用户对服务不同时间段的访问规律,将服务质量的长期变化构建为不定长时间序列模型,该模型能够准确地描述一段时间内用户对服务的真实QoS访问记录。其次,提出一种基于不确定QoS模型的改进遗传算法,该算法采用锦标赛选择策略代替基本遗传算法中的轮盘赌选择策略。最后,在真实数据上进行了大量实验,所提的不定长时间序列模型能够有效地解决不确定QoS感知云服务组合问题,而锦标赛策略的改进遗传算法在寻优结果和稳定性方面均优于基于精英选择策略的遗传算法（E-GA）算法,且运行速度提高近1倍,是可行、高效且稳定的算法。     

Cloud computing service composition: A systematic literature review

The increasing tendency of network service users to use cloud computing encourages web service vendors to supply services that have different functional and nonfunctional (quality of service) features and provide them in a service pool. Based on supply and demand rules and because of the exuberant growth of the services that are offered, cloud service brokers face tough competition against each other in providing quality of service enhancements. Such competition leads to a difficult and complicated process to provide simple service selection and composition in supplying composite services in the cloud, which should be considered an NP-hard problem. How to select appropriate services from the service pool, overcome composition restrictions, determine the importance of different quality of service parameters, focus on the dynamic characteristics of the problem, and address rapid changes in the properties of the services and network appear to be among the most important issues that must be investigated and addressed. In this paper, utilizing a systematic literature review, important questions that can be raised about the research performed in addressing the above-mentioned problem have been extracted and put forth. Then, by dividing the research into four main groups based on the problem-solving approaches and identifying the investigated quality of service parameters, intended objectives, and developing environments, beneficial results and statistics are obtained that can contribute to future research.     

Agent-based multimedia presentation and adaptation service

In this paper, we aim to provide adaptive multimedia services especially video ones to end-users in an efficient and secure manner. Users moving outside the office should be able to maintain an office-like environment at their current locations. First, the agents within our proposed architecture negotiate the different communication and interaction factors autonomously and dynamically. Moreover, we needed to develop a user agent in addition to service and system agents that could negotiate the requirements and capabilities at run time to furnish best possible service results. Thus we designed and integrated a video indexing and key framing service within our overall agent-based architecture. We integrated this video indexing and content-based analysis service to adapt the video content according to run time conditions. We designed a video XML schema to validate the media content out of this multimedia service according to specific requirements and features, as we will describe later.

Cloud service composition of collaborative manufacturing in main manufacturer-suppliers mode for aviation equipment

Manufacturing of aviation equipment is characterized by long R&D cycles, multi-agent collaborations, and high technical difficulties. At present, the main manufacturer-suppliers (M-S) mode is mainly used for the supplier cooperative management of the aviation industry. To realize the efficient collaboration between the main manufacturer and the suppliers in terms of resources, businesses and processes, cloud platforms are gradually applied to the collaborative manufacturing of complex products. In the M-S mode, the manufacturing processes of aviation equipment are characterized by parallel design, multi-agent collaboration, hierarchical management of suppliers and early supplier involvement, which are seldom considered in the existing service composition (SC) methods in the cloud platform. Therefore, a SC model for aviation equipment collaborative manufacturing in the M-S mode (MSCM-SC) is proposed in this paper, in which the subtask correlation and multi-service collaboration are considered. Concurrently, a balance coefficient and a effect factor are put forward to modify the evaluation criteria of service resources, so the calculation method of the objective function can be established. To solve the above model accurately, a multi-layer code is designed and an enhanced carnivorous plant algorithm (ECPA) is proposed. In ECPA, a multi-population strategy and a Cauchy mutation perturbation strategy are developed to improve its exploration ability. Moreover, a variable step size attraction strategy is proposed to improve the exploitation ability of ECPA. Finally, comparative experiments are carried out to verify the effectiveness of ECPA and the MSCM-SC model in this paper. The superiority of ECPA is proved by comparing with several state-of-the-art algorithms by solving 22 classical benchmark test functions, while the effectiveness of the MSCM-SC model is verified by comparison with the traditional SC (T-SC) model on 9 aviation equipment collaborative manufacturing cases with different scales.     

云服务相关问题研究

"云计算"与网络的发展脱不开关系。有线网络的大提速以及无线网络3G乃至4G的普及,共同编织了能让"云"茁壮成长的环境。"网络即电脑"这一概念,现在正从近乎预言的概念慢慢变成现实。在个人应用领域,"云"正以怎样的形式影响日常生活呢?通过对云服务的简要概述,探讨云服务中存在的若干问题。     

Agent-based simulation of competitive and collaborative mechanisms for mobile service chains

A new paradigm for a mobile service chain’s competitive and collaborative mechanism is proposed in this study. The main idea of the proposed approach is based on a multi-agent system with optimal profit of the pull, push, and collaborative models among the portal access service provider (PASP), the product service provider (PSP), and the mobile service provider (MSP). To address the running mechanism for the multi-agent system, an integrated system framework is proposed based on the agent evolution algorithm (AEA), which could resolve all these modes. To examine the feasibility of the framework, a prototype system based on Java-Repast is implemented. The simulation experiments show that this system can help decision makers take the appropriate strategies with higher profits. By analyzing the expectations and variances (or risks) of each player’s profit, the interaction between and among entities in the chain is well understood. It is found that in the situation where a collaborative mechanism is applied, the performance of players is better as compared to the other two situations where a competitive mechanism is implemented. If some constraints are applied, the risk will be kept at a low level.     

Agent-based monitoring service for management of disruptive events in supply chains

Schedules of supply chains are generated with buffers to absorb the effect of disruptive events that could occur during their execution. Schedules can be systematically repaired through specific modifications within buffers by using appropriate decision models that consider the distributed nature of a supply chain. To this aim, information of disruptive events at occurrence or in advance allows decision models to make better decisions. To detect and predict disruptive events along a schedule execution, a service-oriented monitoring subsystem that uses a reference model for defining monitoring models was proposed. This subsystem offers services for collecting execution data of a schedule and environment data, and assessing them to detect/anticipate disruptive events. Because of the distributed nature and the complexity of these services functionalities, this paper presents an agent-based approach for their implementation. This technology allows dealing with supply chain monitoring by structuring monitoring subsystem functionalities as a set of autonomous entities. These entities are able to perform tailored plans created at execution time to concurrently monitor different schedules. A case study is described to try out the implemented prototype system.     

云服务安全性与可靠性的浅析

随着互联网的不断发展盛行,人类社会进入信息化时代.众多先进的信息技术不断被人们应用于生活的各个领域,它们不仅使人们的生活得到了很大改善,为人们的生活提供了很多便利之处,而且让网络技术得到了更广泛地发展、应用.然而,云服务在被人们使用的过程中出现了很多用户信息遗失和泄露等安全风险,云服务的安全性和可靠性受到人们的质疑.本文通过对云服务的安全性和可靠性进行思考,并借由学校云服务的运用探究云服务未来的发展.     

Indeterminacy-aware service selection for reliable service composition

With the development of Internet and Web service technology, Web service composition has been an effective way to construct software applications; service selection is the crucial element in the composition process. However, the existing selection methods mostly generate static plans since they neglect the inherent stochastic and dynamic nature of Web services. As a result, Web service composition often inevitably terminates with failure. An indeterminacy-aware service selection algorithmbased on an improved Markov decision process (IMDP) has been designed for reliable service composition, but it suffers from higher computation complexity. Therefore, an efficient method is proposed, which can reduce the computation cost by converting the service selection problem based on IMDP into solving a nonhomogeneous linear equation set. Experimental results demonstrate the success rate of service composition has been improved greatly, whilst also reducing computation cost.     

Goal-based business service composition

As organizations operate under a highly dynamic business world, they can only survive by optimizing their business processes (BPs) and outsourcing complementary functionality to their core business. To this end, they adopt service-orientation as the underlying mechanism enabling BP optimization and evolution. BPs are now seen as business services (BSs) that span organization boundaries and ought to satisfy cross-organizational objectives. As such, various BS design approaches have been proposed. However, these approaches cannot re-use existing business and software services (SSs) to realize the required BS functionality. Moreover, non-functional requirements and their impact on BS design are not considered. This research gap is covered by a novel, goal-oriented method able to discover those BS and SS compositions fulfilling the required BS functional and non-functional goals at both the business and IT level. This method coherently integrates the design steps involved and properly handles the lack of required BS components. It also advances the state-of-the-art in service composition by being able to both select the best composition plan and the best services realizing the plan tasks based on novel plan and service selection criteria.     

Cloud service selection using cloud service brokers: approaches and challenges

Cloud computing users are faced with a wide variety of services to choose from. Consequently, a number of cloud service brokers (CSBs) have emerged to help users in their service selection process. This paper reviews the recent approaches that have been introduced and used for cloud service brokerage and discusses their challenges accordingly. We propose a set of attributes for a CSB to be considered effective. DifFerent CSBs' approaches are classified as either single service or multiple service models. The CSBs are then assessed, analyzed, and compared with respect to the proposed set of attributes. Based on our studies, CSBs with multiple service models that support more of the proposed effective CSB attributes have wider application in cloud computing environments.     

Cloud federation in a layered service model

We show how a layered Cloud service model of software (SaaS), platform (PaaS), and infrastructure (IaaS) leverages multiple independent Clouds by creating a federation among the providers. The layered architecture leads naturally to a design in which inter-Cloud federation takes place at each service layer, mediated by a broker specific to the concerns of the parties at that layer. Federation increases consumer value for and facilitates providing IT services as a commodity. This business model for the Cloud is consistent with broker mediated supply and service delivery chains in other commodity sectors such as finance and manufacturing. Concreteness is added to the federated Cloud model by considering how it works in delivering the Weather Research and Forecasting service (WRF) as SaaS using PaaS and IaaS support. WRF is used to illustrate the concepts of delegation and federation, the translation of service requirements between service layers, and inter-Cloud broker functions needed to achieve federation.     

Minimum cost service composition in service overlay networks

In service computing, it is often desirable to find the service composition solution for a given service composition request such that the total cost of the service composition solution is minimized. In this paper, we study the problem of finding the minimum cost service composition (MCSC) for a general service composition request which is represented by a directed acyclic graph (DAG). We first prove that the general case of the MCSC problem is NP-Hard. We then show that optimal solutions can be found in polynomial time for some special structured service composition requests. To this end, we derive a sufficient condition on the service composition request graph and propose corresponding algorithms to find the optimal solutions in polynomial time. Using such algorithms as building blocks, we propose heuristic algorithms to decompose the general service composition request graph into service composition request subgraphs with optimal structures. Simulation results demonstrate the effectiveness of the proposed heuristic algorithms.     

基于服务模式的快速服务组合方法研究

多数传统服务组合方法忽视了领域服务的特性,针对特定的领域服务上下文环境时无法进一步提高优化性能,对此提出一种基于模式的快速服务组合方法。分析了领域服务的特征和规律,提出了服务模式的概念。进而给出了一种基于模式的两阶段快速服务组合方法,该方法在第一阶段利用已有的服务模式,采用贪心覆盖策略对用户需求进行快速覆盖,第二阶段则采用原子服务满足第一阶段无法满足的需求。实验表明利用该方法能获得良好的效果和性能。     

QoS-aware and multi-granularity service composition

Composition of Web services can be very complex, and usually involves multiple atomic services and varieties of message exchange patterns. Worst still, with the increasing amount of available services with varying granularity and quality, selecting the best combination of services becomes very challenging. This paper addresses the issues on multi-granularity service composition with awareness of the service quality. In particular, we consider how a new service composition plan is produced, while preserving its original observable behaviors of a service that are shown to the service user, by substituting the service with another service or a set of services of finer or coarser grain. The new plan aims to have services of better quality (if the corresponding underlying services are available). To achieve this, we firstly define a behavioral signature model to capture observable behaviors of services. We then present that two service composition plans are choreography equivalent if they comply with the same behavioral signature model. We then propose a behavioral extracting algorithm to obtain the behavioral signature model from a service composition plan. We also present a method to determine choreography equivalence. Finally we briefly describe our prototype implementation that captures all these proposed algorithms.     

一种面向用户的Web服务组装方法

为了将分布在Internet上异构的Web服务组装成新的服务提供给用户,提出一种面向用户的Web服务组装方法,将组装过程分为需求拆分、服务选择、执行服务组装和服务结果合并四个阶段,并提出了基于组装模式的用户需求输入及拆分方法、基于QoS的服务选择模型和基于中间模式的异构消息转换模型。最后通过物流领域服务组装平台的设计与实现,验证了上述方法的可行性与有效性。     

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.     

基于邻接矩阵的Web服务组合

针对当前Web服务组合方法在动态性和算法时间复杂度方面存在的不足,提出一种基于邻接矩阵的服务组合方法,使用邻接矩阵表示服务间的顺序及并发关系,在构建抽象服务基础上由领域专家初步建立抽象服务的组合关系,利用Warshall算法计算传递闭包来判定服务请求是否可满足,同时构建动态服务组合流程。方法操作简单,Warshall算法时间复杂度为O(n3),在服务组合中有较好的实用性。