AADL模型可靠性分析评估工具

主要针对AADL(architecture analysis and design language)嵌入式系统体系结构进行可靠性建模,实现AADL可靠性模型到广义随机Petri网(general stochastic Petri net,简称GSPN)可靠性计算模型的转换,并基于GSPN可靠性计算模型对嵌入式系统进行...     

多通道压力测试系统Petri网建模及其性能分析

建立了n路多通道压力测试系统的广义随机Petri网(GSPN)模型,利用模型的可达图和MC链分析了GSPN模型的基本性能;推导出了压力测试系统的测试性能的数学公式,测试性能包括各部分的利用率、单位时间内的激发次数、系统时间延迟;并且分析了测试系统各部分之间的相互影响。经过实验验证,证明了该模型的正确性。     

一种AADL系统可靠性模型转换方法

在原有构件依赖关系的基础上,提出一种架构分析与设计语言(AADL)系统可靠性模型的转换方法。该方法对AADL嵌入式系统体系结构进行可靠性建模,实现AADL可靠性模型到广义随机Petri网(GSPN)可靠性计算模型的转换。研究表明,该方法使AADL可靠性模型向GSPN模型的转换规则更加完备,能对嵌入式系统的可靠性进行准确与全面的分析与评估。     

UML活动图到Petri网的转换方法及实现研究

统一建模语言UML缺乏形式化语义,由其描述的模型难以进行动态的分析和验证。而Petri网在具有丰富而严格语义的同时,又有严谨的数学分析方法。综合运用Petri网和UML能够提高软件描述的全面性、一致性、精确性和完整性。研究了UML活动图向Petri网的转换规则,并依据转换规则实现了模型转换工具APConverter。此工具能有效地将活动图转换为Petri网模型并生成PNML文件,进而更好地对UML模型进行分析和验证。     

混合Petri网的流体随机Petri网模型

混合Petri网和流体随机Petri网作为混合系统的建模方法,其内在的建模机制和分析方法不尽相同,而且这两种机制远未发展成熟.分析并建立它们之间相互转换的方法有助于机制本身的发展完善,并利用对方的建模原语和分析方法对系统进行多角度的分析.提出了一阶混合Petri网转换成流体随机Petri网的形式化方法及转换后变迁合并的方法,并给出了转换和合并方法的正确性证明,最后结合实例简要阐述了这两种方法的实现过程.     

基于Petri网的Stateflow建模方法的研究与应用

以输送机器人生产线控制系统设计为例,提出将基于Petri网的Stateflow建模仿真方法应用于PLC控制软件的开发过程中。首先利用Petri网对系统控制功能进行分析,结果表明系统在运行时序上存在并行冲突,采用Petri网的数学建模功能协调冲突后,通过可达图验证了此Petri网模型是安全无死锁的;其次在上述基础上将Petri网与Stateflow组成元素相对应并进行转换;最后利用Simulink构建模型进行系统仿真分析,证明输送机器人生产线控制逻辑正确,状态转移有效。     

UML活动图的正确性检测

UML(统一建模语言)活动图广泛用于软件开发过程,然而它是半形式化的模型,不能进行推理,无法保证其正确性。为了保证它的正确性,必须先把它转化为形式化模型再进行检测。现有工作已将活动图转换成变迁系统、进程代数、Petri网等模型,需要增加或丢失大量信息。本文提出一种新的方法,该方法直接将活动图转换成被称为依赖结构的形式化模型,不会增加或减少活动图的任何信息。基于依赖结构模型我们首先讨论了检测活动图的正确性方法,然后介绍相应的工具;最后用一个实例来详细说明检测过程。该工作有助于软件工程师正确地使用UML活动图对软件系统进行分析和设计。     

无线传感器网络LEACH协议的Petri网模型及性能分析

Petri网是分析网络协议一种有效的形式化建模工具,基于对无线传感器网络LEACH协议运行机制的分析,为协议建立广义随机Petri网(GSPN)性能模型,并用SPNP软件对建立的性能模型进行分析,模型数据验证了模型的有效性,同时讨论了性能模型对协议的低功耗改进所起的指导作用。     

基于GSPN的Web服务组合建模与评价

如何利用广义随机Petri网对WS-BPEL描述语言进行建模、验证以及评价,进而实现对Web服务组合过程可靠性和性能的分析,一直都是领域研究中的难点和热点。首先,给出WS-BPEL业务流程到GSPN的映射规则和转换方法;并通过对GSPN模型进行可达性和不变量分析,实现对WS-BPEL业务流程正确性的验证;然后,借助构造与GSPN模型同构的马尔可夫链,完成对系统性能的分析;最后,以某实例为分析对象,对模型的正确性和有效性进行了验证。     

流体随机Petri网的一阶混杂Petri网模型

为了借用一阶混杂Petri网(First-Order Hybrid Petri Nets)的建模原语和分析方法来分析流体随机Petri网(Fluid Stochastic Petri Nets)以克服流体随机Petri网数值分析方法的局限性,本文提出了一种流体随机Petri网转换成一阶混杂Petri网的形式化描述方法,并对其转换的正确性进行了证明,最后通过实例分析了流体随机Petri网转换成一阶混杂Petri网的必要性.     

QoS assessment via stochastic analysis

Using a stochastic modeling approach based on the Unified Modeling Language and enriched with annotations that conform to the UML profile for schedulability performance, and time, the authors propose a method for assessing quality of service (QoS) in fault-tolerant (FT) distributed systems. From the UML system specification, they produce a generalized stochastic Petri net (GSPN) performance model for assessing an FT application's QoS via stochastic analysis. The ArgoSPE tool provides support for the proposed technique, helping to automatically produce the GSPN model.     

On challenges of model transformation from UML to Alloy

The Unified Modeling Language (UML) is the de facto language used in the industry for software specifications. Once an application has been specified, Model Driven Architecture (MDA) techniques can be applied to generate code from such specifications. Since implementing a system based on a faulty design requires additional cost and effort, it is important to analyse the UML models at earlier stages of the software development lifecycle. This paper focuses on utilizing MDA techniques to deal with the analysis of UML models and identify design faults within a specification. Specifically, we show how UML models can be automatically transformed into Alloy which, in turn, can be automatically analysed by the Alloy Analyzer. The proposed approach relies on MDA techniques to transform UML models to Alloy. This paper reports on the challenges of the model transformation from UML class diagrams and OCL to Alloy. Those issues are caused by fundamental differences in the design philosophy of UML and Alloy. To facilitate better the representation of Alloy concepts in the UML, the paper draws on the lessons learnt and presents a UML profile for Alloy.     

Time scale decomposition of a class of generalized stochastic Petrinet models

A time-scale decomposition (TSD) algorithm of a class of generalized stochastic Petri net (GSPN) models of systems comprising activities whose duration differ by orders of magnitude is presented. The GSPN model of a system can be decomposed into a hierarchical sequence of aggregated subnets, each of which is valid at a certain time scale. These smaller subnets are solved in isolation and their solutions are combined to get the solution of the whole system. A degradable multiprocessor system which would be intractable using conventional techniques, is analyzed using TSD. The complexity of the TSD algorithm can be orders of magnitude smaller without any significant loss in the accuracy of the result. In general, the error due to aggregation is proportional to the maximum degree of coupling between aggregates. An expression of the error due to aggregation is also given in terms of the ratio of fast and slow transitions in the GSPN model. The algorithm is easy to use and can be easily automated     

A combined queueing network and stochastic Petri-net approach for evaluating the performability of fault-tolerant computer systems

In this paper the performability analysis of fault-tolerant computer systems using a hierarchical decomposition technique is presented. A special class of queueing network (QN) models, the so-called BCMP [4], and generalized stochastic Petri nets (GSPN) [1] which are often used to separately model performance and reliability respectively, have been combined in order to preserve the best modelling features of both.

A conceptual model is decomposed into GSPN and BCMP submodels, which are solved in isolation. Then, the remaining GSPN portion of the model is aggregated with flow-equivalents of BCMP models, in order to compute performability measures. The substitutes of BCMP models are presented by means of simple GSPN constructs, thereby preserving the 1st and 2nd moments of the throughput. A simple example of a data communication system where failed transmissions are corrected, is presented.     

一种UML 软件架构性能预测方法及其自动化研究

软件性能需求作为软件质量需求的重要组成部分,已受到人们极大的重视.而只在软件开发周期后期才重点关注软件性能需求的传统软件开发方法,将给开发者带来高风险和高成本等后果.如果能在软件开发周期的早期对软件系统性能进行预测,可以提前发现软件系统架构存在的性能瓶颈,并找出可能的优化方案,对各种设计方案进行比较以得出最优的软件系统架构.研究了一种基于模型的UML 软件架构性能预测方法:该方法选取软件架构设计中的UML 用例图、活动图和构件图,并引入构造型和标记值,将它们扩展为UML SPT 模型;进而,通过转换算法将UML SPT 模型转换为排队网络模型,该算法可处理同时包含分支节点和汇合节点的UML 模型活动图;最后,利用频域分析理论求解排队网络模型,以得出性能参数及性能瓶颈.同时介绍了UML 软件架构性能自动化工具的设计方案,并给出了软件架构性能预测实例.     

UML模型到FSM模型的转换

通常可采用UML的各种图从Web应用不同方面对其进行建模.当对Web应用模型进行测试和验证时,需要分别考虑这些采用了不同图形描述的模型,这就带来了测试和验证的繁琐.如果将UML各种图转换到有限状态机(FSM)模型,则可以统一用FSM模型来表示、验证和测试.提出了基于状态迁移特性保持规则的UML到FSM的模型转换方法,特别针对UML状态图中的3种基本组成单元到FSM模型的转换,给出了各自的转换方法,并实现了原型工具UML2FSM.     

Assessing the understandability of UML statechart diagrams with composite states—A family of empirical studies

The main goal of this work is to present a family of empirical studies that we have carried out to investigate whether the use of composite states may improve the understandability of UML statechart diagrams derived from class diagrams. Our hypotheses derive from conventional wisdom, which says that hierarchical modeling mechanisms are helpful in mastering the complexity of a software system. In our research, we have carried out three empirical studies, consisting of five experiments in total. The studies differed somewhat as regards the size of the UML statechart models, though their size and the complexity of the models were chosen so that they could be analyzed by the subjects within a limited time period. The studies also differed with respect to the type of subjects (students vs. professionals), the familiarity of the subjects with the domains of the diagrams, and other factors. To integrate the results obtained from each of the five experiments, we performed a meta-analysis study which allowed us to take into account the differences between studies and to obtain the overall effect that the use of composite states has on the understandability of UML statechart diagrams throughout all the experiments. The results obtained are not completely conclusive. They cast doubts on the usefulness of composite states for a better understanding and memorizing of UML statechart diagrams. Composite states seem only to be helpful for acquiring knowledge from the diagrams. At any rate, it should be noted that these results are affected by the previous experience of the subjects on modeling, as well as by the size and complexity of the UML statechart diagrams we used, so care should be taken when generalizing our results.     

Towards an Integrated Graph Based Semantics for UML

Recently, we proposed an integrated formal semantics based on graph transformation for central aspects of UML class, object and state diagrams. In this paper, we explain the basic ideas of that approach and show how two more UML diagram types, sequence and collaboration diagrams, can be captured. For UML models consisting of a class diagram and particular state diagrams, a graph transformation system can be defined. Its graphs are associated with system states and its rules with operations in the class diagram and transitions in the state diagrams. Sequence and collaboration diagrams then characterize sequences of operation applications and therefore sequences of transformation rule applications. Thus valid sequence and collaboration diagrams correspond to derivations induced by the graph transformation system. Proceeding this way, it can be checked for example whether such an operation application sequence may be applied in a specific system state.     

Performance analysis of aspect-oriented UML models

Aspect-Oriented Modeling (AOM) techniques allow software designers to isolate and address separately solutions for crosscutting concerns (such as security, reliability, new functional features, etc.). Current AOM research is concerned not only with the separate expression of concerns and their composition into a complete system model, but also with the analysis of different properties of such models. This paper proposes an approach for analyzing the performance effects of a given aspect on the overall system performance, after the composition of the aspect model with the system’s primary model. Performance analysis of UML models is enabled by the “UML Performance Profile for Schedulability, Performance and Time” (SPT) standardized by OMG, which defines a set of quantitative performance annotations to be added to a UML model. The first step of the proposed approach is to add performance annotations to both the primary and the aspect models. An aspect model is generic at first, and therefore its performance annotations must be parameterized. A generic model is converted into a context-specific aspect model with concrete values assigned to its performance annotations. The latter is composed with the primary model, generating a complete annotated UML model. The composition is performed in both structural and behavioural views. A novel approach for composing activity diagrams based on graph-rewriting concepts is proposed in the paper. The next step is to transform automatically the composed model into a Layered Queueing Network (LQN) performance model, by using techniques developed in previous work. The proposed approach is illustrated with a case study system, whose primary model is enhanced with some security features by using AOM. The performance effects of the security aspect under consideration are analyzed in two design alternatives, by solving and analyzing the LQN model of the composed system.