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Research On Software Safety Testing Based On Safety Critical System

Posted on:2017-07-19Degree:MasterType:Thesis
Country:ChinaCandidate:Z X JiFull Text:PDF
GTID:2348330503495754Subject:Computer Science and Technology
Abstract/Summary:PDF Full Text Request
The software of critical systems is much important, if the software failure happens, it may cause greatly personnel injury or property damage.This software is called safety critical software. In order to ensure the safety of the safety critical software, it usually need to safety analysis and safety test. Because the safety critical software is more complexity and more safety, there are many problems of the analysis and test methods now. The safety testing is divorced from the software with the system in some software safety testing method, so it is not comprehensive with analyzing the security of the software. Some safety testing method are testing with not safety analyzing, which is not meet the requirements of completeness and adequacy of the safety, and the the safety requirements are not fully verified. The other safety testing methods are requiring a large number of test cases, and the effective test case reduction methods are not much. In order to solve these problems, the article provides a new framework of the safety testing and analyzing to the safety critical software, and it puts forward a new method in the security analysis, the formation of the generation of test cases and the test strategy. The article's main research content is as follows:(1) Based on the existing safety framework and the rules of the safety testing within the DO-178 B and GJB900-90, this article provides a safety framework which is combining safety analysis and safety testing of safety critical software to solve the problem of incomplete testing.(2) Through analysing the failure reasons of safety critical software, this article puts forward a SHISOM model which is based on FTA and PDG. The model is mainly used to describe interaction between the security behavior of software and system, and the relationship between system risk and software operation. At the same time, the safety requirement of the software is verified. In the model, the execution trajectory graph of the software operation is constructed which is based on the function call graph, it is the basis of the SOSDMG model.At the same time, according to the times of the basic event which is found in dangerous events in dangerous events, calculating the structure importance of basic events.It is foundation of calculating the important degree of software operation and scenario.It is not only considering the contribution to the risk of the software operation in the fault tree,but also combining the structure importance of the software operation in the structure of the software,then the structure importance of the software operation is much real.(3) The SOSDMG model of interaction between software and system is proposed in this article. Firstly, it builds the software scenario which can interactiving with the system, based on the execution trajectory graph of the software operation of the SHISOM model. Secondly, the software scene and the Markov process are combined to construct the SOSDMG interaction model between the software and the system. The structure importance and risk of the software scenario are determined by the importance of the software architecture, the occurrence probability and the hazard degree of the software operation which are based on the SOSDMG model. The concept of safety critical degree is put forward, based on the importance of the structure and risk degree. And the safety testing cases sets are generated based on the safety critical degree of each Markov scenario chain.(4) The safety testing strategy of the software is presented which is combining the degree of safety and reliability of the software, which is based on the SOSDMG mode. At the same time, the safety evaluation method based on scenario and Markov scenario chain are proposed which are based on the SOSDMG model.Finally, through the water cycle in a nuclear reactor cooling control system to verification the feasibility of the model of SHISOM which is based on FTA and PDG, and verify the validity of the SOSDMG model in the development of safety testing cases generation and testing strategy.
Keywords/Search Tags:Safety critical software, fault tree analysis, risk, Markov chain, Software Operation Scenario Dependency Markov Graph(SOSDMG), test strategy
PDF Full Text Request
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