JSP网络故障管理平台(源代码+外文翻译+论文)
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The Survey of Web Service Basede On AutomaticFor the former, one can argue that, in many ways, a composite service issimilar to a workflow 8. The definition of a composite service includes a set ofatomic services together with the control and data flow among the services. Similarly,a workflowhas to specify the flow of work items. The current achievementson flexible workflow, automatic process adaption and cross-enterprise integrationprovide the means for automated Web services composition as well. In addition,the dynamic workflow methods provide the means to bind the abstract nodeswith the concrete resources or services automatically.On the other hand, dynamic composition methods are required to generatethe plan automatically. Most methods in such category are related to AI planningand deductive theorem proving. The general assumption of such kind ofmethods is that each Web service can be specified by its preconditions and effectsin the planning context. Firstly, a Web service is a software componentthat takes the input data and produces the output data. Thus the preconditionsand effects are the input and the output parameters of the service respectively.Secondly, the Web service also alters the states of the world after its execution.So the world state pre-required for the service execution is the precondition, andnew states generated after the execution is the effect. A typical example is aservice for logging into a Web site. The input information is the username andpassword, and the output is a confirmation message. After the execution, theworld state changes from “not logged in” to “logged in”. The “logged in” statewill be keeping until the “log out” service is invoked. If the user can specify thepreconditions and effects required by the composite service, a plan or processis generated automatically by logical theorem prover or AI planners withoutknowledge of predefined workflow. During the planning, the business logic canprovide constraints in the planning setting.In this paper we will present an overview of recent methods that provideautomation to Web service composition. The automation means that either themethod can generate the process model automatically , or the method can locatethe correct services if an abstract process model is given. Some methods based onworkflow have been reported in the work by Benatallah 5, but to our knowledge,no overview on service composition methods related to AI planning has beenpublished yet. As a result, in the paper, we will have more focus on the AIplanning methods than the workflow based methods.This paper is organized as follows. Section 2 presents an abstract frameworkfor Web service composition. Section 3 is the introduction of automatic Webservice composition based on workflow methods. Section 4 provides an overviewand comparison for the selected composition methods based on AI planning. Thelast section concludes the paper. Web Services Composition FrameworkHere, we propose a general framework for automatic Web services composition.This framework is in high-level abstraction, without considering a particularlanguage, platform or algorithm used in composition process. The aim of theframework is to give the basis to discuss similarities and differences of the availableservice composition methods. In addition, we also use the framework tounify the terms used in the paper. A general framework of the service composition system is illustrated in Fig. 1.The composition system has two kinds of participants, service provider and servicerequester. The service providers propose Web services for use. The servicerequesters consume information or services offered by service providers. Thesystem also contains the following components: translator, process generator,evaluator, execution engine and service repository. The translator translates betweenthe external languages used by the participants and the internal languagesused by the process generator. For each request, the process generator tries togenerate a plan that composes the available services in the service repositoryto fulfill the request. If more than one plan is found, the evaluator evaluates allplans and proposes the best one for execution. The execution engine executesthe plan and returns the result to the service provider.Most precisely, the process of automatic service composition includes thefollowing phases:Presentation of single service: firstly, the service providers will advertisetheir atomic services at a global market place. There are several languagesavailable for advertising, for example, UDDI 4 or DAML-S ServicePro-file 14. The essential attributes to describe a Web service include the signature,states and the non-functional values. The signature is represented bythe services inputs, outputs and exceptions. It provides information aboutthe data transformation during the execution of a Web service. The statesare specified by precondition and postcondition. We model it as the transformationfrom one set of states to another in the world. Non-functionalityvalues are those attributes that are used for evaluating the services, such asthe cost, service quality and security issues.Translation of the languages: most service composition systems distinguishbetween the external and internal service specification languages. The externallanguages are used by the service users to enhance accessibility of theusers in the sense that the users can express what they can offer or whatthey want in a relatively easy manner. They are usually different from the internalones that are used by the composition process generator, because theprocess generator requires more formal and precise languages, for example,the logical programming languages. So far, the users have already get usedto the standard Web service languages, such as WSDL and DAML-S. Thusthe translation components between the standardWeb service languages andthe internal languages have to be developed.Generation of composition process model: in the meantime, the servicerequester can also express the requirement in a service specification language.A process generator then tries to solve the requirement by composing theatomic services advertised by the service providers. The process generatorusually takes the functionalities of services as input, and outputs processmodel that describes the composite service. The process model contains aset of selected atomic services and the control flow and data flow amongthese services.Evaluation of composite service: it is quite common that many services havethe same or similar functionalities. So it is possible that the planer generatesmore than one composite service fulfilling the requirement. In that case, thecomposite services are evaluated by their overall utilities using the informationprovided from the non-functional attributes. The most commonly usedmethod is utility functions. The requester should specify weights to eachnon-functionality attributes and the best composite service is the one whois ranked on top.Execution of composite service: after a unique composite process is selected,the composite service is ready to be executed. Execution of a composite Webservice can be thought as a sequence of message passing according to theprocess model. The dataflow of the composite service is defined as the actionsthat the output data of a former executed service transfers to the inputof a later executed atomic service.In the following we will give a survey on the methods used for the processgenerator to generate the process. The methods can be either fully automatedor semi-automated.3 Web Service Composition using Workflow TechniqueIn the workflow-based composition methods, we should distinguish the static anddynamic workflow generation. The static one means that the requester shouldbuild an abstract process model before the composition planning starts. Theabstract process model includes a set of tasks and their data dependency. Eachtask contains a query clause that is used to search the real atomic Web service tofulfill the task. In that case, only the selection and binding of atomic Web serviceis done automatically by program. The most commonly used static method is tospecify the process model in graph. On the other hand, the dynamic compositionboth creates process model and selects atomic services automatically. Thisrequires the requester to specify several constraints, including the dependencyof atomic, the users preference and so on.EFlow7 is a platform for the specification, enactment and management ofcomposite services. EFlow uses a static workflow generation method. A compositeservice is modeled by a graph that defines the order of execution amongthe nodes in the process. The graph is created manually but it can be updateddynamically. The graph may include service, decision and event nodes. Servicenodes represent the invocation of an atomic or composite service, decision nodesspecify the alternatives and rules controlling the execution flow, and event nodesenable service processes to send and receive several types of events. Arcs in thegraph denote the execution dependency among the nodes. Although the graphshould be specified manually, EFlow provides the automation to bind the nodeswith concrete services. The definition of a service node contains a search recipethat can be used to query actual service either at process instantiation time or atruntime. As the service node is started, the search recipe is executed, returninga reference to a specific service. In particular, the search recipe is resolved eachtime when a service node is activated. They do so because the availability of servicesmay change very frequently in a highly dynamic environment. In 8, theauthors further refine the service composition platform and propose a prototypeof composite service definition language(CSDL). An interesting feature of CSDLis that it distinguishes between invocation of services and operations within aservice. It provides the adaptive and dynamic features to cope with the rapidlyevolving business and IT environment in which Web services are executed.Polymorphic Process Model (PPM)23 uses a method that combines thestatic and dynamic service composition. The static setting is supported by referenceprocess-based multi-enterprise processes, the processes that consist ofabstract subprocesses, i.e., subprocesses that have functionality description butlack implementation. The abstract subprocesses are implemented by service andbined at runtime. This is similar to the service binding in EFlow. The dynamicpart of PPM is supported by service-based processes. Here, a service is modeledby a state machine that specifies that possible states of a service and their transitions.Transitions are caused by service operation(also called service activity)invocations or internal service transitions. In the setting, the dynamic servicecomposition is enabled by the reasoning based on state machine.基于自动化技术的Web Service的研究在这篇文章中，我们主要提出了一些最新的将自动化用于Web service组成的方法。这里的自动化意思是方案能自动产生过程模型，或如果抽象过程模型已给出，方案就能查找到合适的服务。Benatallah5提出了一些基于工作流的方案。但是据我们的知识，现在还没有一个和人工智能相关的关于服务组成方案的概述发表出来。因此，我们在人工智能方案上要比基于工作流的方案投入更多的注意力。在从前很多方面，人们可能讨论一个组成服务和一个工作流8很相似。组成服务的定义包括自动服务的建立和服务间控制和数据的传递。相似的，一个工作流程详细说明了工作项目的流程。现在在这种灵活的工作流程中取得的成绩，自动过程的适应，跨企业的整合同样也为自动化Web service组成提供了方案。另外，动态的工作流程方法也提供了连接抽象的节点和具体资源或自动服务的工具。另一方面，动态的组成方法被用来自动的产生方案。在这个类别的大多数方法和人工智能计划、演绎法证明相关。这种方法一般假设每一个Web service由计划的前提和结果来确定。首先，Web service是一个软件，它会接受输入的数据和产生输出的数据。因此，前提和结果就分别是服务的输入，输出参数。第二，Web service也在执行以后改变系统的状态。所以，系统的状态预先要求服务执行是前提，新的状态在执行后产生是结果。一个典型的例子是登陆网页的服务，输入的信息是用户名和密码，输出是确认的信息。执行完毕后，系统状态就会由未登录变成登录。登录的状态会一直保持到调用离开系统服务。如果用户能指出组成服务要求的前提和结果，那么运用逻辑定理证明或人工智能计划，而不需要预先确定的工作流程知识，一个计划或是一个过程就会自动产生了。在这个计划中，业务逻辑会在计划制定中产生一些约束。这篇文章的内容如下,第二部分讲述了Web service组成的大概框架，第三部分介绍了基于工作流方案的自动化Web service组成。Web service组成框架这里，我们提出了一个关于自动Web service组成的一般框架。这个框架是一个高层的抽象，它不考虑合成进程中特殊的语言，平台或算法。这个框架的目的是给出一个讨论相似和不同的有用服务组成方案的基本参考。除此之外，我们还用框架来统一文章中用到的项目。一般服务组成系统的框架见fig.1。这个组成系统有两个参与者：服务提供者和服务请求者。服务提供者提供Web service供使用，服务请求者使用服务商提供的信息或服务。这个系统也包含了下面一些组成部分：翻译器、进程生成器、评估器、执行器和服务库。翻译器将参与者使用的其他的语言翻译成进程生成器使用的内部语言。对每一个请求，进程生成器都尽力产生一个计划在服务库里组成一个有用的服务来执行请求。如果找到了多个计划，鉴别器就执行计划并将结果返回给服务提供者。更准确的说，自动化服务组成的过程包括以下一些短语：单服务显示：首先，服务提供者会在全球市场上宣传他们的原子服务。这就需要有多种可用的语言来做宣传。比如说，UDDI4或DAML-S Service Profile14。描述Web service的本质特征包括签名、状态、无函数值。签名由服务的输入、输出和异常来表示出来。它提供了在Web service的执行中数据转换的信息。状态由前提条件和后置条件来说明。我们把它作为模型，将一个状态的设置转换成其他的状态。无函数值有些特征，这些特征用来评价服务，比如成本、服务质量和安全问题。语言翻译：大多数服务组成系统在外部和内部服务规范语言不同。在某种程度上，使用服务的用户用外部语言加强用户的可访问性，使用户能用一个相关简单的方法表达出什么是他们能提供的和什么是他们想要的。这些语言通常和合成进程生成器使用的内部的语言不同，因为这个进程产生器要求更多的正式和精确的语言，比如说逻辑程序设计语言。到现在为止，用户已经习惯了标准Web service的语言，如WSDL和DAML-S。因此，标准Web service语言和内部语言之间的转换成分还需要发展。合成进程模型的产生：服务请求者也能用服务规范语言表达
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