基于PETRI网的语义WEB服务组合建模及可靠性研究

发布时间：2018-03-02 15:21

本文选题：OWL-S　切入点：服务组合　出处：《重庆大学》2014年硕士论文　论文类型：学位论文

【摘要】：如今，Internet为我们提供了可供访问的大量的Web服务，这些服务大多面向特定的功能，而且单个服务能完成的工作是很有限的。如果能够找到一种方法，让我们可以以一种机器可理解的方式对Web服务进行描述，进而把功能相对单一的服务进行组合，我们就能在不必大量编写代码的情况下获得增值服务，这就是语义Web研究的问题。 OWL-S是最有效的语义Web服务本体语言之一，它提供了一种基于本体的框架和规则，在这种规则下对Web服务的描述具有语义信息，可以使计算机在一定程度上理解我们的描述。OWL-S语言使用方便、表达能力强，并且对Web服务的描述非常清晰明了。但是，目前在语义本体语言方面的理论研究重在其形式化和性质验证，而在非功能特性和量化分析方面却相对薄弱。为了使用户能判断一个服务在非功能特性方面是否能满足其需求，进而从服务群中选出对其整体系统最有利的服务，我们需要建立一种方法来分析OWL-S中组合服务的服务质量。在这篇论文中，我们以非马尔科夫链的随机Petri网（NMSPN）为基础，对OWL-S中涉及的原子服务、结构服务建立了Petri网模型，从而可以方便地使用基于概率的方法计算单个服务的正常结束概率，然后通过计算得到整个系统的可靠性。这种方法使用一个概率性的值来表示服务调用和SOAP消息传递的成功情况，并将其作为输入参数传入模型进行计算。为了验证模型和计算方法的可行性与正确性，我们详细分析了一个实例。先建立起系统的Petri网模型，然后测得它在实际运行中的各种数据。使用这些数据计算出系统的可靠性之后，，又对计算结果进行了置信区间分析。在论文的最后部分，我们还进行了参数的灵敏度实验，经过分析就可以知道实例系统中哪个服务的哪一项指标是影响系统可靠性的关键，然后就可以重点对这一个模块进行优化，从而提升整个系统的可靠性。
[Abstract]:Today, the Internet provides us with a large number of Web services that are accessible, most of which are oriented to specific functions, and where there is limited work that a single service can do. So that we can describe Web services in a machine-understandable way, and then combine relatively single services, we can get value-added services without having to write a lot of code. This is the problem of semantic Web research. OWL-S is one of the most effective semantic Web services ontology languages. It provides an ontology-based framework and rules, in which the description of Web services has semantic information. Can make the computer understand our description to some extent. OWL-S language is easy to use, strong expressive ability, and the description of Web services is very clear. At present, the theoretical research on semantic ontology language focuses on its formalization and nature verification, but it is relatively weak in non-functional characteristics and quantitative analysis. In order to enable users to judge whether a service can meet its needs in non-functional features, Furthermore, we need to establish a method to analyze the service quality of composite services in OWL-S. In this paper, we establish a Petri net model for atomic services and structural services in OWL-S based on random Petri nets with non-Markov chains. Thus, it is easy to use probability-based methods to calculate the normal end probability of a single service. Then, the reliability of the whole system is obtained by calculation, which uses a probabilistic value to express the success of service invocation and SOAP messaging, and passes it into the model as an input parameter. In order to verify the feasibility and correctness of the model and calculation method, we analyze an example in detail. First, the Petri net model of the system is established. The reliability of the system is calculated by using these data, and then the confidence interval analysis of the results is made. In the last part of the paper, the sensitivity experiments of the parameters are also carried out. Through analysis, we can know which index of which service is the key to the reliability of the system, and then we can optimize the module to improve the reliability of the whole system.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP393.09

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