地图符号服务与地图服务的耦合

为了实现地图符号在地图服务(WMS)中的应用,达到灵活定制WMS可视化效果的目的,从支持WMS的图层样式描述规范(SLD)入手,通过对SLD和WMS的分析,研究网络地图符号的发布方法,设计地图符号服务框架,提出了基于SLD,地图符号服务与WMS的耦合方法,以解决基于WMS的WebGIS应用中无法通过符号改变地图可视化效果的问题,实验结果表明该方法可以有效地关联地图符号服务与WMS,实现了WMS可视化效果的灵活定制.     

通用远程过程调用的设计与实现

在分布式计算系统中，远程过程调用ＲＰＣ是种流行的进程间通信机制。ＲＰＣ简单灵活，且功能较强。上前大多数ＲＰＣ机制是同步的，严重地影响了分布式应用的并行性。我们设计和实现了一个通用的ＲＰＣ。本文讨论了设计的要点和方法，并对通用ＲＰＣ的实现作了介绍。     

有关远程过程调用的几个重要问题的讨论

远程过程调用作为构造分布式系统的一个重要工具已经得到了广泛的应用,本文详细讨论了有关ＲＰＣ的七个重要问题：网络传输协议、类型一致性、错误处理、孤儿问题、效率问题、性能问题、互操作性。     

CoRAL: A transparent fault-tolerant web service

The Web is increasingly used for critical applications and services. We present a client-transparent mechanism, called CoRAL, that provides high reliability and availability for Web service. CoRAL provides fault tolerance even for requests being processed at the time of server failure. The scheme does not require deterministic servers and can thus handle dynamic content. CoRAL actively replicates the TCP connection state while maintaining logs of HTTP requests and replies. In the event of a primary server failure, active client connections fail over to a spare, where their processing continues seamlessly. We describe key aspects of the design and implementation as well as several performance optimizations. Measurements of system overhead, failover performance, and preliminary validation using fault injection are presented.     

Security by typing

We present an approach for analyzing cryptographic protocols that are subject to attack from an active intruder who takes advantage of knowledge of the protocol rules. The approach uses a form of type system in which types are communication steps and typing constraints characterize all the messages available to the intruder. This reduces verification of authentication and secrecy properties to a typing problem in our type system. We present the typing rules, prove soundness of a type inference algorithm, and establish the correctness of the typing rules with respect to the protocol execution and intruder actions. The protocol specifications used in the approach can be automatically extracted from the conventional, informal cryptographic protocol notation commonly found in the literature. To validate the approach, we implement our algorithm in a tool called DYMNA, which is a practical and efficient environment for the specification and analysis of cryptographic protocols.     

WSB: a broker‐centric framework for quality‐driven web service discovery

Web service interfaces can be discovered through several means, including service registries, search engines, service portals, and peer‐to‐peer networks. But discovering Web services in such heterogeneous environments is becoming a challenging task and raises several concerns, such as performance, reliability, and robustness. In this paper, we introduce the Web Service Broker (WSB) framework that provides a universal access point for discovering Web services. WSB uses a crawler to collect the plurality of Web services disseminated throughout the Web, continuously monitor the behavior of Web services in delivering the expected functionality, and enable clients to articulate service queries tailored to their needs. The framework features ranking algorithms we have developed which are capable of ranking services according to Quality of Web Service parameters. WSB can be seamlessly integrated into the existing service‐oriented architectures. Copyright © 2010 John Wiley & Sons, Ltd.     

A systematic literature review on web service clustering approaches to enhance service discovery,selection and recommendation

With the advancement of web 2.0 and the development of the Internet of Things (IoT), all tasks can be handled with the help of handheld devices. Web APIs or web services are providing immense power to IoT and are working as a backbone in the successful journey of IoT. Web services can perform any task on a single click event, and these are available over the internet in terms of quantity, quality, and variety. It leads to the requirement of service management in the service repository. The well-managed and structured service repository is still challenging as services are dynamic, and documentation is limited. It is also not a piece of cake to discover, select and recommend services easily from a pool of services. Web service clustering (WSC) plays a vital role in enhancing the service discovery, selection, and recommendation process by analyzing the similarity among services. In this paper, with a systematic process total of 84 research papers are selected, and different state-of-the-art techniques based on web service clustering are investigated and analyzed. Furthermore, this Systematic Literature Review (SLR) also presents the various mandatory and optional steps of WSC, evaluation measures, and datasets. Research challenges and future directions are also identified, which will help the researchers to provide innovative solutions in this area.     

Quality of service for workflows and web service processes

Workflow management systems (WfMSs) have been used to support various types of business processes for more than a decade now. In workflows or Web processes for e-commerce and Web service applications, suppliers and customers define a binding agreement or contract between the two parties, specifying quality of service (QoS) items such as products or services to be delivered, deadlines, quality of products, and cost of services. The management of QoS metrics directly impacts the success of organizations participating in e-commerce. Therefore, when services or products are created or managed using workflows or Web processes, the underlying workflow engine must accept the specifications and be able to estimate, monitor, and control the QoS rendered to customers. In this paper, we present a predictive QoS model that makes it possible to compute the quality of service for workflows automatically based on atomic task QoS attributes. We also present the implementation of our QoS model for the METEOR workflow system. We describe the components that have been changed or added, and discuss how they interact to enable the management of QoS.     

A framework for the deployment of adaptable web service compositions

The basic paradigm of service-oriented architectures—publication, discovery, and use—can be interpreted in different ways. Current technologies assume a static and rigid approach: UDDI was conceived with the idea of a centralized repository for service publication and BPEL only supports design–time bindings between the orchestrated workflow and the external services. The trend, however, is towards more flexibility and dynamism. The single centralized repository is being substituted by dedicated repositories that cooperate and exchange information about stored services on demand. Design–time compositions are complemented by mechanisms to allow for the selection and binding of services at runtime. This paper presents the research results of our group in delivering a framework for the deployment of adaptable Web service compositions. The publication infrastructure integrates existing heterogeneous repositories and makes them cooperate for service discovery. The deployment infrastructure supports BPEL-like compositions that can select services dynamically, and also adjust their behavior in response to detected changes and unforeseen events. The framework also provides a monitoring-based validation of running compositions: we provide suitable probes to oversee the execution of deployed compositions. The various parts of the framework are exemplified on a common case study taken from the automotive domain. This research is partially supported by the European IST project SeCSE (Service Centric System Engineering) and the Italian FIRB project ARTDECO (Adaptive infRasTructures for DECentralized Organizations).     

Non-redundant web services composition based on a two-phase algorithm

Recently, there has been growing interest in developing web services composition search systems. Current solutions have the drawback of including redundant web services in the results. In this paper, we proposed a non-redundant web services composition search system called NRC, which is based on a two-phase algorithm. In the NRC system, the Link Index is built over web services according to their connectivity. In the forward phase, the candidate compositions are efficiently found by searching the Link Index. In the backward phase, the candidate compositions decomposed into several non-redundant web services compositions by using the concept of tokens. Results of experiments involving data sets with different characteristics show the performance benefits of the NRC techniques in comparison to state-of-the-art composition approaches.     

The practical application of a process for eliciting and designing security in web service systems

Best practices currently state that the security requirements and security architectures of distributed software-intensive systems should be based on security risk assessments, which have been designed from security patterns, are implemented in security standards and are tool-supported throughout their development life-cycle. Web service-based information systems uphold inter-enterprise relations through the Internet, and this technology has been revealed as the reference solution with which to implement Service-Oriented Architectures. In this paper, we present the application of the Process for Web Service Security (PWSSec), developed by the authors, to a real web service-based case study. The manner in which security in inter-organizational information systems can be analyzed, designed and implemented by applying PWSSec, which combines a risk analysis and management, along with a security architecture and a standard-based approach, is also shown. We additionally present a tool built to provide support to the PWSSec process.     

A computing coordination based fuzzy group decision-making (CC-FGDM) for web service oriented architecture

As the demands for faster data processing and enterprise computing are increasing, the traditional client/server architecture has gradually been replaced by Grid computing or the peer-to-peer (P2P) model which can share the content or resources over the network. In this paper, a new computing architecture – computing power services (CPS) – has been applied to utilize web services and business process execution language for overcoming the issues about flexibility, compatibility and workflow management. CPS is a lightweight web services based computing power-sharing architecture, and suitable for enterprise computing tasks which can be executed in the batch processes within a trusty network. However, a real-time load balance and dispatching mechanism is needed for distributed-computing architecture like CPS in order to handle computing resources efficiently and properly. Therefore, a fuzzy group decision-making based adaptive collaboration design for CPS is proposed in this paper to provide the real-time computation coordination and quality of service. In this study, the approach has been applied to analyze the robustness of digital watermark by filter bank selection and the performance can be improved in the aspect of speedup, stability and processing time. This scheme increases the overall computing performance and shows stability for the dynamic environment.     

Meta web service: building web-based open decision support system based on web services

Web services are currently one of the trends in network-based business services, which intuitively will be applied to build a semantic web-based decision support system (DSS). Since web services are self-contained, modular business process applications, based on open standards, enable integration models for facilitating program-to-program interactions. Decision modules in a semantic web-based DSS can be viewed as a web service. However, according to the current features, web services know only about themselves, they are neither autonomous, nor are they designed to use ontologies; they are passive until invoked, and they do not provide for composing functionalities. These lead to the motivation on building a sophisticated web service to contain these features and to utilize web services on behalf of the user. This paper aims to propose a new concept of Meta Web Service, a web service-based DSS. The meta web service understands the user's problem statement with ontology, performs web service discovery, web service composition, and automatically generates codes for composite web service execution. Case-based reasoning is applied to quickly find past histories of successful service compositions. A prototype of research web service has been developed to show the feasibility of the proposed idea.     

The peregrine high-performance RPC system

The Peregrine RPC system provides performance very close to the optimum allowed by the hardware limits, while still supporting the complete RPC model. Implemented on an Ethernet network of Sun-3/60 workstations, a null RPC between two user-level threads executing on separate machines requires 573μs. This time compares well with the fastest network RPC times reported in the literature, ranging from about 1100 to 2600 μs, and is only 309 μs above the measured hardware latency for transmitting the call and result packets in our environment. For large multi-packet RPC calls, the Peregrine user-level data transfer rate reaches 8.9 Mbit/s, approaching the Ethernet's 10 Mbit/s network transmission rate. Between two user-level threads on the same machine, a null RPC requires 149 μs. This paper identifies some of the key performance optimizations used in Peregrine, and quantitatively assesses their benefits.     

Modeling and verifying choreographed multi-agent-based web service compositions regulated by commitment protocols

The competency to compose web services from available services is one of the most crucial problems in the paradigm of service-oriented computing. Conventional software engineering approaches and even standard languages compose web services as workflow models that control the business logic required to coordinate data over participating services. Such models would not apply to the design of multi-agent based web services, which offer high-level abstractions that support autonomy, business-level compliance, and flexible dynamic changes. In this article, we model interactions among multi-agent based web services by commitment modalities in the form of contractual obligations and devote multi-agent commitment protocols to regulate such interactions and engineer services composition. We develop and fully implement an automatic verifier by enriching the MCMAS model checker with certain symbolic algorithms to verify the correctness of protocols, given properties expressed in a temporal commitment logic, suitably extended with actions. We analyze the time and space complexity of the verifier. Finally, we present the experimental results of two case studies, adopted to check the verifier’s efficiency and scalability.     

A simple system for constructing distributed,mixed-language programs

The Mixed-Language Programming (MLP) System is a simple system that facilitates construction of sequential programs in which procedures can be written in different programming languages to exploit heterogeneity in language functionality. In addition, MLP provides a simple remote procedure call (RPC) facility that allows heterogeneity in machine functionality to be exploited. To minimize implementation cost, the system does not solve all of the problems related to mixed-language programming; rather, MLP is designed to handle common situations well. Among the unique aspects of MLP are its advanced facilities, which allow complex situations to be handled with user intervention; for example, these facilities allow arguments of a type not defined by a language to be used by procedures written in that language. This paper overviews the use of MLP and describes its implementation. In addition, two programs that have been written using the MLP system—a small database system and a collection of plot routines—are discussed. The system executes on a collection of Vaxes and Suns running Berkeley UNIX. Currently supported languages are C, Pascal and Icon.     

Remote rendezvous

BNR Pascal is a systems programming language intended for the implementation of the systems software of distributed computing systems. It supports the Ada Rendezvous model of tasking and communication, uniformly extended to support communications between tasks distributed over the computing nodes of a system. BNR Pascal was designed and implemented in 1980, and has since been used to implement the operating systems and real-time applications software for Northern Telecom's Meridian family of products. In total, more than 2 million lines of BNR Pascal exist. This paper describes the BNR Pascal remote rendezvous: the extension of rendezvous to interprocessor communication. It discusses the implementation of remote rendezvous, describing the advantages and disadvantages of several options. Finally, it details BNR's experience in using remote rendezvous in building substantial, practical distributed systems used in products.