QoS-aware middleware for Web services composition

The paradigmatic shift from a Web of manual interactions to a Web of programmatic interactions driven by Web services is creating unprecedented opportunities for the formation of online business-to-business (B2B) collaborations. In particular, the creation of value-added services by composition of existing ones is gaining a significant momentum. Since many available Web services provide overlapping or identical functionality, albeit with different quality of service (QoS), a choice needs to be made to determine which services are to participate in a given composite service. This paper presents a middleware platform which addresses the issue of selecting Web services for the purpose of their composition in a way that maximizes user satisfaction expressed as utility functions over QoS attributes, while satisfying the constraints set by the user and by the structure of the composite service. Two selection approaches are described and compared: one based on local (task-level) selection of services and the other based on global allocation of tasks to services using integer programming.     

Development of Web-Telecom based hybrid services orchestration and execution middleware over convergence networks

Influenced by the success of Web service technologies for development and deployment of IT services, Telecom R&D community starts to adapt and build similar service delivery platforms, trying to manage the hard constraints in Telecom domains, such as existence of heterogeneous protocols, extensive use of asynchronous communications and real-time delivery requirements, which will open a new paradigm for Web service based voice over IP communication and also can be easily integrated in end-to-end SOA solutions. In this paper, we study both the Web-Telecom based hybrid services orchestration and execution middleware for coordinating existing Telecom services and IT services. In particular, we focus on the design and implementation Web-Telecom based hybrid service bus (WTSB), event-driven Telecom service engine (EDLE) and also the integration layer for the messages dispatching and transformation between WTSB and EDLE, which can make the EDLE service engine seamlessly integrated into WTSB. More specifically, with multimedia conferencing scenarios, we demonstrate how our hybrid services orchestration and execution middleware orchestrate multimedia conferencing communication services together, and also make performance measurement and analysis. Finally, we give the conclusions and future work.     

Efficient execution of composite Web services exchanging intensional data

Web service technologies provide a standard means of integrating heterogeneous applications distributed over the Internet. Successive compositions of new Web services using pre-existing ones usually create a hierarchical structure of invocations among a large number of Web services. For the efficient execution of these composite Web services, we propose an approach which exploits intensional XML data, i.e. an XML document that contains special elements representing the calls to Web services, in order to delegate the invocations of the external Web services to some relevant nodes. We formalize an invocation plan for composite Web services in which intensional data is used as their parameters and results, and define a cost-based optimization problem to obtain an efficient invocation plan for them. We provide an A∗ heuristic search algorithm to find an optimal invocation plan for a given set of Web services and also present a greedy method of generating an efficient solution in a short time. The experimental results show that the proposed greedy method can find a close-to-optimal solution efficiently and has good scalability for a complex call hierarchy of Web services.     

基于服务QoS执行信息的Web服务推荐研究

基于服务的非功能（QoS）特性进行服务发现是面向服务计算领域的一个研究热点。为了克服服务QoS难以获取且动态变化的特点,提出一种基于已往QoS执行信息的Web服务推荐方法。首先给出一种可以方便记录QoS执行信息的系统框架;然后描述了基于时间加权的服务推荐的匹配算法;实验结果表明该推荐方法是可行和有效的。     

Web服务组合执行引擎中服务异步调用机制研究*

研究了BPEL4WS执行引擎WebJetFlow对Web服务的异步调用机制,在引擎的服务调用代理中对Web服务统一采用非阻塞双传输异步调用,提高了调用线程的利用率。同时引入了cache机制并设计了相应的cache替换算法,保证了引擎对异步调用结果消息的匹配效率以及数据安全性, 通过实验验证引擎的性能有了明显的提高。     

FENECIA: failure endurable nested-transaction based execution of composite Web services with incorporated state analysis

Interest in the Web services (WS) composition (WSC) paradigm is increasing tremendously. A real shift in distributed computing history is expected to occur when the dream of implementing Service-Oriented Architecture (SOA) is realized. However, there is a long way to go to achieve such an ambitious goal. In this paper, we support the idea that, when challenging the WSC issue, the earlier that the inevitability of failures is recognized and proper failure-handling mechanisms are defined, from the very early stage of the composite WS (CWS) specification, the greater are the chances of achieving a significant gain in dependability. To formalize this vision, we present the FENECIA (Failure Endurable Nested-transaction based Execution of Composite Web services with Incorporated state Analysis) framework. Our framework approaches the WSC issue from different points of view to guarantee a high level of dependability. In particular, it aims at being simultaneously a failure-handling-devoted CWS specification, execution, and quality of service (QoS) assessment approach. In the first section of our framework, we focus on answering the need for a specification model tailored for the WS architecture. To this end, we introduce WS-SAGAS, a new transaction model. WS-SAGAS introduces key concepts that are not part of the WS architecture pillars, namely, arbitrary nesting, state, vitality degree, and compensation, to specify failure-endurable CWS as a hierarchy of recursively nested transactions. In addition, to define the CWS execution semantics, without suffering from the hindrance of an XML-based notation, we describe a textual notation that describes a WSC in terms of definition rules, composability rules, and ordering rules, and we introduce graphical and formal notations. These rules provide the solid foundation needed to formulate the execution semantics of a CWS in terms of execution correctness verification dependencies. To ensure dependable execution of the CWS, we present in the second section of FENECIA our architecture THROWS, in which the execution control of the resulting CWS is distributed among engines, discovered dynamically, that communicate in a peer-to-peer fashion. A dependable execution is guaranteed in THROWS by keeping track of the execution progress of a CWS and by enforcing forward and backward recovery. We concentrate in the third section of our approach on showing how the failure consideration is trivial in acquiring more accurate CWS QoS estimations. We propose a model that assesses several QoS properties of CWS, which are specified as WS-SAGAS transactions and executed in THROWS. We validate our proposal and show its feasibility and broad applicability by describing an implemented prototype and a case study.     

Achieving middleware execution efficiency: hardware-assisted garbage collection operations

Although virtualization technologies bring many benefits to cloud computing environments, as the virtual machines provide more features, the middleware layer has become bloated, introducing a high overhead. Our ultimate goal is to provide hardware-assisted solutions to improve the middleware performance in cloud computing environments. As a starting point, in this paper, we design, implement, and evaluate specialized hardware instructions to accelerate GC operations. We select GC because it is a common component in virtual machine designs and it incurs high performance and energy consumption overheads. We performed a profiling study on various GC algorithms to identify the GC performance hotspots, which contribute to more than 50% of the total GC execution time. By moving these hotspot functions into hardware, we achieved an order of magnitude speedup and significant improvement on energy efficiency. In addition, the results of our performance estimation study indicate that the hardware-assisted GC instructions can reduce the GC execution time by half and lead to a 7% improvement on the overall execution time.     

GMarte: Grid middleware to abstract remote task execution

Grid computing technologies are now being largely deployed with the widespread adoption of the Globus Toolkit as the industrial standard Grid middleware. However, its inherent steep learning curve discourages the use of these technologies for non‐experts. Therefore, to increase the use of Grid computing, it is important to have high‐level tools that simplify the process of remote task execution. In this paper we introduce a middleware, developed on top of the Java Commodity Grid, which offers an object‐oriented, user‐friendly application programming interface, from the Java language, which eases remote task execution for computationally intensive applications. Copyright © 2006 John Wiley & Sons, Ltd.     

Application execution management on the InteGrade opportunistic grid middleware

The InteGrade project is a multi-university effort to build a novel grid computing middleware based on the opportunistic use of resources belonging to user workstations. The InteGrade middleware currently enables the execution of sequential, bag-of-tasks, and parallel applications that follow the BSP or the MPI programming models.     

Using a cloud-centric middleware to enable mobile hosting of Web services: mHealth use case

The unceasing growth and divergence of the mobile landscape have led to the use of smartphone and tablet devices in consuming Web services (WS) in enterprises. However, in heterogeneous WS, the shift from the mobile client consumer approach to the mobile service hosting approach is insufficiently studied. With the advancement of storage and processing capabilities of these devices, coupled with the high availability of the Web, this research focuses on the use of the mobile devices as hosts of WS in a mHealth domain. In this paper, a cloud-centric middleware technique is employed to enable access to the mobile hosts. The paper presents mobile hosting of medical data which are modeled as light-weight WS which is deployed in a real-world system. Further, a workflow authorization model is proposed to ensure privacy and the prevention of unauthorized modification of data on the mobile hosts. A data encryption technique is also put forward to enforce security and privacy of the mobile hosted data. Our current implemented project, called SOPHRA, supports mobile communication over HTTP in a Wi-Fi environment.     

基于语义的Web服务自动发现、匹配及执行平台

基于UDDI技术的普遍的Web服务发现、匹配、执行平台有可能产生严重的效率及服务响应延迟问题，文中介绍了一个限定于特定领域的Web服务自动发现、匹配及执行系统以试图解决此问题，同时给出了一个基于OWL-S本体语言的系统实现。在服务选择过程中实现了地域匹配功能，并为服务请求代理提供了一个初步的行为记忆功能。     

Multi-mode interaction middleware for software services

Due to the independency, variability, and tailorability of software service in the open environment, the research of middleware which supports software services multi-mode interaction is thus of great importance. In this paper, an agent-based multi-mode interaction middleware model and its supporting system for software services were proposed. This model includes an interaction feature decomposition and configuration model to enable interaction programming, an agent-based middleware model, and a programmable coordination media based on reflection technology. The decomposition and configuration model for interaction features can assist programmers in interaction programming by analyzing and synthesizing interaction features. The agent-based middleware model provides a runtime framework for service multi-mode interaction. The programmable coordination media is able to effectively support software service coordination based on multimode interaction. To verify feasibility and efficiency of the above method, the design, implementation and performance analysis of Artemis-M3C, a multi-mode interaction middleware for software services, were introduced. The result shows that the above method is feasible and that the Artemis-M3C system is practical and effective in multi-mode interaction.     

Integration with Web services

There's a difference between what we'd like our enterprise computing systems to be and what they really are. We like to envision them as orderly multitier arrangements comprising software buses, hubs, gateways, and adapters - all deployed at just the right places to maximize scale, load, application utility, and ultimately, business value. Unfortunately, we know that there's a wide gulf between this idealistic vision and reality. In practice, our enterprise computing systems typically are tangles of numerous technologies, protocols, and applications, often hastily hard-wired together with inflexible point-to-point connections. The whole point of middleware is to hide the diversity and complexity of the computing machinery underneath it. By adopting the abstractions that middleware provides, we're supposedly isolating our applications from the variety of ever-changing hardware platforms, operating systems, networks, protocols, and transports that make up our enterprise computing systems. We can use Web services to provide "middleware for middleware" abstraction layer for modern integration applications.     

Bounding completion times of jobs with arbitrary release times,variable execution times and resource sharing

The workload of many real time systems can be characterized as a set of preemptable jobs with linear precedence constraints. Typically their execution times are only known to lie within a range of values. In addition, jobs share resources and access to the resources must be synchronized to ensure the integrity of the system. The paper is concerned with the schedulability of such jobs when scheduled on a priority driven basis. It describes three algorithms for computing upper bounds on the completion times of jobs that have arbitrary release times and priorities. The first two are simple but do not yield sufficiently tight bounds, while the last one yields the tightest bounds but has the greatest complexity     

Distributed middleware architectures for scalable media services

The fusion of Multimedia and Internet technology has introduced an ever-increasing demand for large-scale reliable media services. This exposes the scalability limitations of current middleware architectures, as they traditionally operate on either very large-server configurations or on tightly coupled distributed systems. On the other hand, the wide availability of high-speed networks and the widespread deployment of powerful personal computing units by end users, has emphasized the advantages of the peer-to-peer (P2P) computing model. In this paper, we evaluate a number of different middleware architectures that facilitate the timely and reliable delivery of media services in P2P networks. Our evaluated architectures exploit features including availability of high-performance links, replication and caching of popular items and finally state-of-the-art search techniques proposed in the context of structured and unstructured P2P overlay networks. Through detailed simulation we investigate the behavior of the suggested P2P architectures for video provision and examine the involved trade-offs. We show that under realistic assumptions, the evaluated architectures are resilient to multiple peer-failures, are scalable with respect to dropped requests when the number of messages in the network increases and provide good response times to the user requests.     

Improving prediction of computational job execution times with machine learning

Predicting resource consumption and run time of computational workloads is crucial for efficient resource allocation, or cost and energy optimization. In this paper, we evaluate various machine learning techniques to predict the execution time of computational jobs. For experiments we use datasets from two application areas: scientific workflow management and data processing in the ALICE experiment at CERN. We apply a two-stage prediction method and evaluate its performance. Other evaluated aspects include: (1) comparing performance of global (per-workflow) versus specialized (per-job) models; (2) impact of prediction granularity in the first stage of the two-stage method; (3) using various feature sets, feature selection, and feature importance analysis; (4) applying symbolic regression in addition to classical regressors. Our results provide new valuable insights on using machine learning techniques to predict the runtime behavior of computational jobs.     

Pipelined processors and worst case execution times

The calculation of worst case execution time (WCET) is a fundamental requirement of almost all scheduling approaches for hard real-time systems. Due to their unpredictability, hardware enhancements such as cache and pipelining are often ignored in attempts to find WCET of programs. This results in estimations that are excessively pessimistic. In this article a simple instruction pipeline is modeled so that more accurate estimations are obtained. The model presented can be used with any schedulability analysis that allows sections of nonpreemptable code to be included. Our results indicate the WCET overestimates at basic block level can be reduced from over 20% to less than 2%, and that the overestimates for typical structured real-time programs can be reduced by 17%–40%.     

语义Web服务——Web服务的扩展

语义Web服务是应用语义Web技术对Web服务的扩展.使信息具有语义就是用计算机内的Ontology中的概念作标记符对信息进行标记,对该过程予以支持的就是语义Web技术,即Ontology的构建技术、Ontology的使用技术(语义推理技术)和信息的语义标记技术.语义Web技术对Web服务的扩展可具体化为两项任务:服务提供者、服务请求者和服务注册处三类服务主体均内置Ontology;发布、查找和绑定三种交互信息均采用语义标记.