基于Petri网的Web服务流程建模方法研究

随着网络应用的蓬勃发展,Web服务越来越普及。在实际应用中,往往需要对已有Web服务进行集成。目前通常的企业Web服务集成过程,都是先根据企业的业务流程建立相应的Web服务流程模型,再由此建立应用系统。而目前已有的建模手段的共同问题是：无法确保模型的正确性和与具体业务的紧密吻合。该文提出一种基于Petri网的Web服务流程建模方法。该建模方法通过将Petri网引入建模过程弥补了原建模过程中无法直观感受模型的不足,通过建立一套完备的形式化定义保证了建立模型的正确性,通过将紧同步随机Petri网引入建模过程可以更好的描述实际业务。通过使用该方法, 可以很好地解决现在Web流程建模过程中存在的问题。此方法也为其他领域中的流程建模仿真提供了一种很好的解决问题的方法和思路。

基于JavaScript的浏览器端调用Web服务研究与实现

根据WebOffice系统中浏览器-服务器端通信需求,提出了一种调用Web服务的浏览器端代理方法.比较了此方法和传统的服务器端方法的优点和缺点,分析了此方法的适用场合.最后给出了实现的要点:WSDL的加载和解析、对象类型的序列化和反序列化、SOAP协议的封包和绑定.

语义Web中描述逻辑本体的可伸缩推理和非一致处理

随着Web信息的与日俱增，使用机器处理这种信息成为一种必然的趋势。语义Web应运而生，成为当前研究的热点之一。它以本体为核心，为不同领域提供共享的词汇，以便机器处理Web信息。表达本体的标准语言OWL以描述逻辑为基础。OWL本体的推理可伸缩性差，难以适应规模较大的本体应用，因此推理可伸缩性问题是一个重要的实际问题。此外，OWL本体是一个逻辑系统，在生成、维护和集成等过程中，都很容易出现非一致现象，导致标准的推理机制不能正常运作。因此本体非一致问题是另一个重要的实际问题。针对上述两个实际问题，本文分别在实现可伸缩推理、修复非一致本体、以及进行非一致容忍推理三个方面提出了解决办法。 [可伸缩推理方面] 本文提出了一种本体断言公理集的划分方法，使本体推理能够在独立的划分子集中进行，以此提高本体推理的可伸缩性。 [本体修复方面] 本文提出了一种计算具有最小删除代价的本体子集的方法；通过删除这种本体子集，可以恢复本体的一致性。该方法将计算上述本体子集的问题归约为在命题逻辑程序中计算某种最优模型的问题，以调用现有的可满足性问题求解器来解决。 [非一致容忍推理方面] 本文将命题逻辑中字典序推理方法应用到描述逻辑中，以提供针对非一致本体的查询机制。本文还提出了一种在描述逻辑本体中进行字典序推理的方法。该方法将字典序结论的判定问题归约为命题可满足性判定问题，以调用现有的可满足性问题求解器来解决。

基于状态方面的Web服务动态替换

随着面向服务计算技术的成熟,服务复合已成为Internet上开发企业间业务协作的一种新模式,WS-BPEL是服务复合事实上的标准.但是由于复合服务所依赖的第三方伙伴服务的分布、自治和松散耦合等特性,在执行过程中易受到伙伴服务失效的影响,可靠性无法得到保证,因此需要支持在运行时对伙伴服务进行动态替换.目前的BPEL规范只提供有限的服务替换功能,当与伙伴服务的交互涉及到一系列有状态的会话操作时,服务替换就更加复杂.通过对面向方面的研究,提出面向BPEL语言的状态方面扩展.通过状态方面,记录与伙伴服务交互过程中的会话信息.在伙伴服务失效时,通过透明地替换伙伴服务,使得与当前伙伴服务的会话信息传播到功能等价的另一个伙伴服务上,以保证流程的正常执行.通过该方法,使得BPEL流程具有一定的自愈能力,增强了流程执行的可靠性.

基于语义的Web服务匹配及其框架模型研究

随着Internet上异构应用系统的大量增加和SOA技术的空前发展，Web服务技术变得越来越重要，已经成为了学术界和工业界关注的热点。在Web服务技术中，服务发现为Web服务消费者调用Web服务提供者提供的服务提供了桥梁，起到非常重要的承接作用，成为了Web服务技术中的重点。目前的Web服务发现机制主要有两种，第一种是传统的Web服务发现方式，主要基于UDDI（Universal Description， Discovery and Integration）的纯粹关键字查找；第二种是基于Web服务的语义信息，进行Web服务间的语义匹配。 第一种方法的基础UDDI是国际标准，而且应用也最为广泛，但UDDI中对于Web服务的描述是基于语法的，而且缺乏Web服务所特有的I/O属性和服务质量属性等信息。第二种方法基于Web服务的语义信息，包括Web服务所特有的I/O属性，但因为缺乏灵活有效的Web服务匹配方法和与之对应的Web服务匹配框架，限制了其应用。 基于此，本文在对当前语义Web服务匹配技术分析和研究的基础上，对当前的语义Web服务匹配方法进行了改进，同时提出了基于过滤器（filter）的语义Web服务匹配框架模型。本文的主要工作有： 1）对目前的语义Web服务匹配技术进行了较为全面深入的探讨和综述。 2）对当前的语义Web服务匹配的各个阶段进行了详细的分析，对其中的匹配方法进行了改进。提出了基于向量空间模型(VSM)和TF-IDF(Term Frequency–Inverse Document Frequency)思想的本体权重的计算方法，本体层次关系图中边的权重的计算方法和本体之间相似度的计算方法。 3）提出了基于web服务黑盒属性的语义。 4）语义Web服务匹配框架方面，本文提出了基于filter的语义Web服务匹配框架，并将其延伸到非语义Web服务系统中。

语义Web中的自动推理和主动规则终止性分析

语义Web是现有Web的一个语义延伸，目标是使Web的应用具有一定的智能，能够进行更准确的信息搜索和一定的决策支持，帮助用户自动完成一些任务。语义Web的实现需要人工智能、数据库等领域的技术支持，需要对已有的技术进行改进和扩展，也需要对现有技术本身如ECA规则进行更深入的研究从而进一步将其扩展到语义Web。自动推理技术是语义Web实现的基础之一，而ECA规则可以为系统增加反应性行为能力，本文围绕自动推理和ECA规则，主要进行了如下研究：（1） 一阶逻辑推理技术对语义Web的推理支持。分析了语义Web语言需要的表达能力，对现有描述逻辑工具、一阶逻辑工具的能力进行了考察。现有的描述逻辑工具不足以处理应用所需要的更丰富的语言成分、任意的一阶逻辑规则等，而一阶逻辑自动定理证明工具和有限模型查找工具有分别都有较好的研究成果。把语义Web的推理问题化成可满足性判定问题后，本文给出了一阶逻辑定理证明器和有限模型查找器形成的并发过程进行可满足性判定的方法。这样既可以解决描述逻辑工具的不足，并可弥补定理证明器对可满足的公式推理的不完备性。（2） ECA规则(主动规则)的终止性分析。终止性是主动规则最重要的行为性质，不终止是由于主动规则的级联触发造成的，意味着定义错误。终止性检查通常是不可判定的。有效的静态分析方法是主动规则得以实际应用的保证。静态分析的关键是合适的数据库状态描述，本文给出用约束表示数据库状态的方法，通过模拟规则执行，使用约束求解进行条件计算和重复状态检查，判断主动规则集合是否终止。用约束精确表示了数据库状态，在规则处理中考虑了执行语义，从而得到更精确的终止性结论。

Web-based spatiotemporal visualization of marine environment data

With long-term marine surveys and research, and especially with the development of new marine environment monitoring technologies, prodigious amounts of complex marine environmental data are generated, and continuously increase rapidly. Features of these data include massive volume, widespread distribution, multiple-sources, heterogeneous, multi-dimensional and dynamic in structure and time. The present study recommends an integrative visualization solution for these data, to enhance the visual display of data and data archives, and to develop a joint use of these data distributed among different organizations or communities. This study also analyses the web services technologies and defines the concept of the marine information gird, then focuses on the spatiotemporal visualization method and proposes a process-oriented spatiotemporal visualization method. We discuss how marine environmental data can be organized based on the spatiotemporal visualization method, and how organized data are represented for use with web services and stored in a reusable fashion. In addition, we provide an original visualization architecture that is integrative and based on the explored technologies. In the end, we propose a prototype system of marine environmental data of the South China Sea for visualizations of Argo floats, sea surface temperature fields, sea current fields, salinity, in-situ investigation data, and ocean stations. An integration visualization architecture is illustrated on the prototype system, which highlights the process-oriented temporal visualization method and demonstrates the benefit of the architecture and the methods described in this study.

Changes in Web Client Access Patterns: Characteristics and Caching Implications

Understanding the nature of the workloads and system demands created by users of the World Wide Web is crucial to properly designing and provisioning Web services. Previous measurements of Web client workloads have been shown to exhibit a number of characteristic features; however, it is not clear how those features may be changing with time. In this study we compare two measurements of Web client workloads separated in time by three years, both captured from the same computing facility at Boston University. The older dataset, obtained in 1995, is well-known in the research literature and has been the basis for a wide variety of studies. The newer dataset was captured in 1998 and is comparable in size to the older dataset. The new dataset has the drawback that the collection of users measured may no longer be representative of general Web users; however using it has the advantage that many comparisons can be drawn more clearly than would be possible using a new, different source of measurement. Our results fall into two categories. First we compare the statistical and distributional properties of Web requests across the two datasets. This serves to reinforce and deepen our understanding of the characteristic statistical properties of Web client requests. We find that the kinds of distributions that best describe document sizes have not changed between 1995 and 1998, although specific values of the distributional parameters are different. Second, we explore the question of how the observed differences in the properties of Web client requests, particularly the popularity and temporal locality properties, affect the potential for Web file caching in the network. We find that for the computing facility represented by our traces between 1995 and 1998, (1) the benefits of using size-based caching policies have diminished; and (2) the potential for caching requested files in the network has declined.

Phylotastic! Making tree-of-life knowledge accessible, reusable and convenient.

BACKGROUND: Scientists rarely reuse expert knowledge of phylogeny, in spite of years of effort to assemble a great "Tree of Life" (ToL). A notable exception involves the use of Phylomatic, which provides tools to generate custom phylogenies from a large, pre-computed, expert phylogeny of plant taxa. This suggests great potential for a more generalized system that, starting with a query consisting of a list of any known species, would rectify non-standard names, identify expert phylogenies containing the implicated taxa, prune away unneeded parts, and supply branch lengths and annotations, resulting in a custom phylogeny suited to the user's needs. Such a system could become a sustainable community resource if implemented as a distributed system of loosely coupled parts that interact through clearly defined interfaces. RESULTS: With the aim of building such a "phylotastic" system, the NESCent Hackathons, Interoperability, Phylogenies (HIP) working group recruited 2 dozen scientist-programmers to a weeklong programming hackathon in June 2012. During the hackathon (and a three-month follow-up period), 5 teams produced designs, implementations, documentation, presentations, and tests including: (1) a generalized scheme for integrating components; (2) proof-of-concept pruners and controllers; (3) a meta-API for taxonomic name resolution services; (4) a system for storing, finding, and retrieving phylogenies using semantic web technologies for data exchange, storage, and querying; (5) an innovative new service, DateLife.org, which synthesizes pre-computed, time-calibrated phylogenies to assign ages to nodes; and (6) demonstration projects. These outcomes are accessible via a public code repository (GitHub.com), a website (http://www.phylotastic.org), and a server image. CONCLUSIONS: Approximately 9 person-months of effort (centered on a software development hackathon) resulted in the design and implementation of proof-of-concept software for 4 core phylotastic components, 3 controllers, and 3 end-user demonstration tools. While these products have substantial limitations, they suggest considerable potential for a distributed system that makes phylogenetic knowledge readily accessible in computable form. Widespread use of phylotastic systems will create an electronic marketplace for sharing phylogenetic knowledge that will spur innovation in other areas of the ToL enterprise, such as annotation of sources and methods and third-party methods of quality assessment.

BioHackathon series in 2011 and 2012: penetration of ontology and linked data in life science domains.

The application of semantic technologies to the integration of biological data and the interoperability of bioinformatics analysis and visualization tools has been the common theme of a series of annual BioHackathons hosted in Japan for the past five years. Here we provide a review of the activities and outcomes from the BioHackathons held in 2011 in Kyoto and 2012 in Toyama. In order to efficiently implement semantic technologies in the life sciences, participants formed various sub-groups and worked on the following topics: Resource Description Framework (RDF) models for specific domains, text mining of the literature, ontology development, essential metadata for biological databases, platforms to enable efficient Semantic Web technology development and interoperability, and the development of applications for Semantic Web data. In this review, we briefly introduce the themes covered by these sub-groups. The observations made, conclusions drawn, and software development projects that emerged from these activities are discussed.

A framework for collaborative working environments

To utilize the advantages of existing and emerging Internet techniques and to meet the demands for a new generation of collaborative working environments, a framework with an upperware–middleware architecture is proposed, which consists of four layers: resource layer, middleware layer, upperware layer and application layer. The upperware contains intelligent agents and plug/play facilities; the former coordinates and controls multiple middleware techniques such as Grid computing, Web-services and mobile agents, while the latter are used for the applications, such as semantic CAD, to plug and loose couple into the system. The method of migrating legacy software using automatic wrapper generation technique is also presented. A prototype mobile environment for collaborative product design is presented to illustrate the utilization of the CWE framework in collaborative design and manufacture.

A Web-Service Based Approach for Software Sharing

A Web-service based approach is presented which enables geographically dispersed users to share software resources over the Internet. A service-oriented software sharing system has been developed, which consists of shared applications, client applications and three types of services: application proxy service, proxy implementation service and application manager service. With the aids of the services, the client applications interact with the shared applications to implement a software sharing task. The approach satisfies the requirements of copyright protection and reuse of legacy codes. In this paper, the role of Web-services and the architecture of the system are presented first, followed by a case study to illustrate the approach developed.

Analysing Web-Orchestrations Under Stress Using Uncertainty Profiles

An orchestration is a multi-threaded computation that invokes a number of remote services. In practice, the responsiveness of a web-service fluctuates with demand; during surges in activity service responsiveness may be degraded, perhaps even to the point of failure. An uncertainty profile formalizes a user's perception of the effects of stress on an orchestration of web-services; it describes a strategic situation, modelled by a zero-sum angel–daemon game. Stressed web-service scenarios are analysed, using game theory, in a realistic way, lying between over-optimism (services are entirely reliable) and over-pessimism (all services are broken). The ‘resilience’ of an uncertainty profile can be assessed using the valuation of its associated zero-sum game. In order to demonstrate the validity of the approach, we consider two measures of resilience and a number of different stress models. It is shown how (i) uncertainty profiles can be ordered by risk (as measured by game valuations) and (ii) the structural properties of risk partial orders can be analysed.