A fuzzy Petri net-based expert system and its application to damageassessment of bridges

In this paper, a fuzzy Petri net approach to modeling fuzzy rule-based reasoning is proposed to bring together the possibilistic entailment and the fuzzy reasoning to handle uncertain and imprecise information. The three key components in our fuzzy rule-based reasoning-fuzzy propositions, truth-qualified fuzzy rules, and truth-qualified fuzzy facts-can be formulated as fuzzy places, uncertain transitions, and uncertain fuzzy tokens, respectively. Four types of uncertain transitions-inference, aggregation, duplication, and aggregation-duplication transitions-are introduced to fulfil the mechanism of fuzzy rule-based reasoning. A framework of integrated expert systems based on our fuzzy Petri net, called fuzzy Petri net-based expert system (FPNES), is implemented in Java. Major features of FPNES include knowledge representation through the use of hierarchical fuzzy Petri nets, a reasoning mechanism based on fuzzy Petri nets, and transformation of modularized fuzzy rule bases into hierarchical fuzzy Petri nets. An application to the damage assessment of the Da-Shi bridge in Taiwan is used as an illustrative example of FPNES.     

模糊Petri网在带权不精确知识表示和推理中的应用研究

Petri网是一种适合于描述异步并发事件的计算机系统模型 ,可以有效地对并行和并发系统进行形式化验证和行为分析 .以模糊 Petri网的基本定义为基础 ,讨论了带权模糊知识的模糊产生式系统表示法 ,建立了这种表示法与模糊 Petri网之间的映射关系和转换算法 ;在对模糊 Petri网进一步扩充的基础上 ,解决了与知识的模糊Petri网表示相关的几个问题 ;最后给出了模糊 Petri网中不确定性的计算方法和相应的不精确推理算法     

A reasoning algorithm for high-level fuzzy Petri nets

We introduce an automated procedure for extracting information from knowledge bases that contain fuzzy production rules. The knowledge bases considered here are modeled using the high-level fuzzy Petri nets proposed by the authors in the past. Extensions to the high-level fuzzy Petri net model are given to include the representation of partial sources of information. The case of rules with more than one variable in the consequent is also discussed. A reasoning algorithm based on the high-level fuzzy Petri net model is presented. The algorithm consists of the extraction of a subnet and an evaluation process. In the evaluation process, several fuzzy inference methods can be applied. The proposed algorithm is similar to another procedure suggested by Yager (1983), with advantages concerning the knowledge-base searching when gathering the relevant information to answer a particular kind of query     

INFERENCE PROCEDURES FOR FUZZY KNOWLEDGE REPRESENTATION SCHEME

This article presents a formal model of the knowledge representation scheme based on the fuzzy Petri net (FPN) theory. The model is represented as a 13-tuple consisting of the components of the FPN, two functions that give semantic meanings to the scheme and a set of contradictions. For the scheme, called the knowledge representation scheme based on the fuzzy Petri nets theory (KRFPN) the fuzzy inheritance and fuzzy recognition-inference procedures based on the dynamical properties of the FPN, are described in detail. The upper-time complexity of both the proposed inference algorithms is O(nm), where n is the number of places (concepts) and m is the number of transitions (relations) in the scheme. Illustrative examples of the fuzzy inheritance and the fuzzy recognition algorithms for the knowledge base, designed by the KRFPN, are given.     

基于扩展模糊Petri网的知识推理方法研究

为使模糊Petri网能够描述可变模糊隶属判据下的模糊知识,利用基准变换能较好地表达模糊隶属判据可变情况的特点,基于定性映射和定性基准变换对模糊Petri网进行了扩展,给出了扩展后网模型的形式定义和基本运行机制。通过利用定性映射描述模糊产生式规则,给出了一种新的知识表示模式和推理方法,新方法有利于构建模糊Petri网基于认知的学习机制。结果显示,该网模型具有较强的知识表达能力,适用于处理认知模糊不确定性知识,其推理过程能体现某些认知特性,尤其适用于构建以定性判断为特点的智能系统。     

复杂网络安全事件的知识表示和关联分析方法

针对复杂网络安全事件信息的模糊性和不确定性的推理问题,提出采用一种加权模糊Petri网的安全事件知识表示和关联分析的方法.将Petri网和加权模糊产生式方法结合起来,通过引入网络安全事件征兆权值的概念,用权值大小来描述多个安全事件征兆对安全事件发生的贡献程度.在一定程度上有效地解决网络安全事件之间的复杂因果关系推理及不确定知识的表示问题.     

Timed high-level nets

Petri nets have been widely used for modeling and analyzing concurrent systems. Several reasons contribute to their success: the simplicity of the model, the immediate graphical representation, the easy modeling of asynchronous aspects, the possibility of reasoning about important properties such as reachability, liveness, boundedness. However, the original model fails in representing two important features: complex functional aspects, such as conditions which rule the flow of control, and time. Due to that, two different classes of extensions of Petri nets have been proposed: high-level nets and timed Petri nets. High-level nets allow the representation of functional aspects in full details, but do not provide a means for representing time; on the other hand, timed Petri nets have been thought for time representation, but they do not provide a means for representing detailed functinal aspects. Thus, these two important aspects cannot be mastered together. In particular, it is difficult to express relationships between time and functional aspects.This paper investigates the relationships between high-level nets and timed Petri nets, thus extending a first set of results published in a previous paper, where a unifying Petri net based model for time representation has been proposed. It first recalls how time can be represented in a Petri net extension called ER nets, and assesses its generality. It then investigates the relationships of ER nets with the best known high-level nets. In particular it shows the overall equivalence of ER nets, Colored Petri nets and Predicate/Transition nets, and extends the mechanism for time representation introduced in ER nets to both Colored Petri nets and Predicate/Transition nets. It also shows that these models cannot be simplified without significantly constraining the timing aspects that can be modeled.     

动态模糊Petri网模型及其应用研究

以模糊Petri网的基本定义，动态模糊集和动态模糊逻辑为基础，讨论了动态模糊Petri网的基本模型，建立了动态模糊Petri网与模糊Petri网之间的映射关系和转移算法，解决了与动态模糊知识的动态模糊Petri网表示相关的几个问题，最后给出了动态模糊Petri网中动态模糊性的计算方法和相应的推理方法。     

应用带标识的模糊Petri网的知识表示方法

提出一种在某些库所中带有标识的模糊Petri网模型来进行知识表示。为了获得更多的加权模糊产生式规则的信息,在知识表示的过程中考虑了权值,确定性因子,阈值等参数。这种模糊Petri网充分利用了Petri网的并行处理能力。随着带标识的模糊Petri网的运行,网中标识的变化可以标记加权模糊推理的运行。通过文中给出的基于相似性测度的计算方法可以更加高效地计算出多层加权模糊推理的推理结果。     

应用带标识的模糊Petri网的模糊推理

本文针对模糊推理中常存在推理结果意义不明确的问题,提出应用带标识的模糊Petri网(MFPNs)进行模糊推理。推理的过程中考虑模糊产生式规则的权值、阈值、确定性因子等几种知识表示参数以获得更多信息。给出基于相似性测度的模糊推理算法,通过计算带标识的模糊Petri网的最终输出库所中的托肯值可以得到最终的模糊推理结果。通过实例可以验证这样得到的推理结果意义更明确,计算过程更加高效。     

一种模糊Petri网的逆向知识推理方法设计实现

模糊Petri网是模糊产生式知识表示和推理的理想工具.针对基于模糊产生式规则的知识库,在已知决策目标的前提下,设计了该知识库的模糊Petri网模型及基于递归的逆向知识推理方法,并以实例时该方法进行了验证.对于任意指定的库所,通过该方法可以确定其模糊托肯值,即对应命题的模糊真值.该方法的逻辑表达力强,利于计算机实现,而且其逆向推理策略能有效减少计算空间,使计算在一个复杂的模糊Petri网系统的子系统中进行,提高了计算效率.     

模糊Petri网及知识表示

在建造专家系统中虽然有很多种知识表示方法，但都有不尽人意的地方，本文试图用一种新的方法－Ｐｅｔｒｉ网模型来表示知识。本文给出了Ｆｕｚｚｚｙ Ｐｅｔｒｉ网和广义Ｆｕｚｚｙ Ｐｅｔｒｉ网两种模型，并给出了相应的推理算法，一旦专家知识用Ｐｅｔｒｉ网表示后，根据Ｐｅｔｒｉ网固有的特性，我们就能处理专家系统中并行推理、无回溯推理，反向推理等问题。     

基于模糊Petri网的汽车故障诊断仿真研究

本文将Petri网和模糊推理相结合,建立故障诊断的模糊Petri网模型。其中,用FPN表示模糊产生规则,用Petri网的变迁激活规则进行故障诊断推理,从而分析出异常行为过程间的因果关系,推理出故障的原因及其可信度。以汽车故障诊断为例,建立了基于模糊Petri网的诊断模型。通过仿真分析,验证了模型的正确性和算法的有效性。     

一种改进的基于规则的带权模糊推理算法

给出了一种基于带权模糊Petri网的模糊推理算法，这种算法可以适用于一类基于规则的系统，即可以对该类系统的带权模糊Petri网模型进行相应的处理。对系统建立了知识表示的带权模糊Petri网模型，使用该算法可以确定用户给定的库所之间是否存在联系，即相应的命题之间是否存在因果关系，可以计算出命题的模糊真值。对具体的算例进行了分析并与已有的算法进行了比较，得出该算法的优点。     

模糊Petri网知识表示方法在入侵检测中的应用

根据网络攻击具有并发性,攻击特征的提取具有不确定性等特点,给出了采用模糊Pelri网实现攻击知识的表达和入侵检测的推理模型。该模型解决了误用入侵检测系统中现有知识表示方法不能并行推理的问题,以及传统的基于Pelri网可达图搜索求解导致模型描述复杂、推理缺少智能的问题。最后通过入侵实例验证了该模型的正确性和有效性。     

一种自适应模糊Petri网及其应用*

模糊Petri网(fuzzy Petri nets, FPN)是基于模糊产生式规则的知识库系统的有力建模工具,但其缺乏较强的自学习能力。在FPN的基础上引入神经网络技术,给出了一种自适应模糊Petri网(adapt fuzzy Petri nets, AFPN)模型。该模型将神经网络中的BP网络算法引入到FPN模型中,对FPN中的权值进行反复的学习训练,避免了依靠人工经验设置带来的不确定性。AFPN具有很强的推理能力和自适应能力,对知识库系统的建立、更新和维护有着重要的意义。     

基于模糊神经Petri网的故障诊断模型

Petri网是对具有产生式规则的故障诊断系统的有力建模工具，但其缺乏较强的学习能力．本文以Petri网的基本定义为基础，结合模糊逻辑和Petri网模型，定义了模糊Petri网模型，在此基础上引入人工神经网络技术，给出了人工神经网络的模糊Petri网表示方法，并针对工程机械故障诊断异步、离散等特点，提出并建立了故障诊断的模糊神经Petri网模型及其改进模型．基于模糊神经Petri网的故障诊断系统结合了Petri网和人工神经网络的优点，经过自学习后同时具有很强的推理能力和自适应能力．     

Knowledge representation-oriented nets for discrete event systemapplications

This paper presents knowledge representation-oriented nets (KRON), a knowledge representation schema for discrete event systems (DES). KRON enables the representation and use of a variety of knowledge about a DES static structure and its dynamic states and behavior. It is based on the integration of high-level Petri nets with frame-based representation techniques and follows the object-oriented paradigm. The main objective considered in its definition is to obtain a comprehensive and powerful representation model for data and control of DES. The use of the DES behavioral knowledge is governed by a control mechanism stored in a separate inference engine. KRON provides an efficient execution mechanism to make the models evolve. This is an adaptation of the RETE matching algorithm in order to deal with the features provided by high-level Petri nets and it takes advantage of its integration with a frame/object-oriented representation schema, Moreover, KRON facilitates dealing with decision points in the execution of nondeterministic models. A prototype of a simulation tool with graphical display and animation facilities has been implemented for KRON and it has been used in several case studies in the manufacturing systems domain     

模糊Petri网在航电总线系统故障诊断中的研究

航电总线系统结构复杂,各部件相互耦合,故障传播模式多样化。因此,为了处理故障诊断中不充分和模糊的信息,提出了将模糊Petri网应用到航电总线系统的故障诊断中,构建出其故障的传播模型,并在模型的基础上,给出有效的推理算法。表明利用模糊Petri网,可以建立航电总线系统的故障传播模式的模型,清晰地反映故障的产生、发展及影响。