軟件過程與管理chapter16軟件質(zhì)量保證

1、1chapter 16n軟件質(zhì)量保證軟件質(zhì)量保證齊大計控學院吳迪討論n軟件質(zhì)量保證為什么重要？軟件質(zhì)量保證為什么重要？3什么是軟件質(zhì)量？nphil crosby once said:nthe problem of quality management is not what people dont know about it. the problem is what they think they do know . . . in this regard, quality has much in common with sex. neverybody is for it. (under cer

2、tain conditions, of course.) neveryone feels they understand it. (even though they wouldnt want to explain it.) neveryone thinks execution is only a matter of following natural inclinations. (after all, we do get along somehow.) nand, of course, most people feel that problems in these areas are caus

3、ed by other people. (if only they would take the time to do things right.)416.2elements of sqanstandards nreviews and audits ntestingnerror/defect collection and analysis nchange management neducation nvendor management nsecurity management nsafety nrisk management 16.3.1 軟件質(zhì)量保證的任務(wù)n編制項目質(zhì)量保證計劃；編制項目質(zhì)量

4、保證計劃；n參與項目的軟件過程的描述編寫；參與項目的軟件過程的描述編寫；n評審軟件工程活動，以驗證是否符合規(guī)評審軟件工程活動，以驗證是否符合規(guī)定的軟件過程；定的軟件過程；n審核指定的軟件工作產(chǎn)品以驗證是否遵審核指定的軟件工作產(chǎn)品以驗證是否遵守作為軟件過程一部分的哪些規(guī)定。守作為軟件過程一部分的哪些規(guī)定。n確保根據(jù)文檔化的規(guī)程記錄和處理軟件確保根據(jù)文檔化的規(guī)程記錄和處理軟件工作和工作產(chǎn)品中的偏差；工作和工作產(chǎn)品中的偏差；n記錄各種不符合項報告給高層管理人員記錄各種不符合項報告給高層管理人員；6role of the sqa group-inprepares an sqa plan for a p

5、roject. nthe plan identifies evaluations to be performed audits and reviews to be performed standards that are applicable to the project procedures for error reporting and tracking documents to be produced by the sqa group amount of feedback provided to the software project teamnparticipates in the

6、development of the projects software process description. n the sqa group reviews the process description for compliance with organizational policy, internal software standards, externally imposed standards (e.g., iso-9001), and other parts of the software project plan.8role of the sqa group-iinrevi

7、ews software engineering activities to verify compliance with the defined software process. n identifies, documents, and tracks deviations from the process and verifies that corrections have been made.naudits designated software work products to verify compliance with those defined as part of the so

8、ftware process. nreviews selected work products; identifies, documents, and tracks deviations; verifies that corrections have been maden periodically reports the results of its work to the project manager.nensures that deviations in software work and work products are documented and handled accordin

9、g to a documented procedure.nrecords any noncompliance and reports to senior management.nnoncompliance items are tracked until they are resolved.討論n如果客戶不斷改變他想做的事情，如果客戶不斷改變他想做的事情，是否還有可能評估軟件質(zhì)量？是否還有可能評估軟件質(zhì)量？n為什么軟件工程小組與獨立的軟件為什么軟件工程小組與獨立的軟件質(zhì)量保證小組的關(guān)系經(jīng)常是緊張的質(zhì)量保證小組的關(guān)系經(jīng)常是緊張的？n這種緊張關(guān)系是否是正常的？這種緊張關(guān)系是否是正常的？1216.3.

10、2 sqa goals nrequirements quality. the correctness, completeness, and consistency of the requirements model will have a strong influence on the quality of all work products that follow. ndesign quality. every element of the design model should be assessed by the software team to ensure that it exhib

11、its high quality and that the design itself conforms to requirements.ncode quality. source code and related work products (e.g., other descriptive information) must conform to local coding standards and exhibit characteristics that will facilitate maintainability.nquality control effectiveness. a so

12、ftware team should apply limited resources in a way that has the highest likelihood of achieving a high quality result.1416.5 statistical sqameasurement. an understanding of how to improve quality .collect information on all defectsfind the causes of the defectsmove to provide fixes for the process1

13、516.5 statistical sqaninformation about software errors and defects is collected and categorized.nan attempt is made to trace each error and defect to its underlying cause .nusing the pareto principle (80 percent of the defects can be traced to 20 percent of all possible causes), isolate the 20 perc

14、ent (the vital few).nonce the vital few causes have been identified, move to correct the problems that have caused the errors and defects.n已經(jīng)證明統(tǒng)計軟件質(zhì)量保證技術(shù)已經(jīng)證明統(tǒng)計軟件質(zhì)量保證技術(shù)確實質(zhì)量提高，某些情況下，軟確實質(zhì)量提高，某些情況下，軟件組織已經(jīng)去得了每年減少件組織已經(jīng)去得了每年減少51%缺陷的好成績。缺陷的好成績。n統(tǒng)計統(tǒng)計sqa及及pareto原則的應(yīng)用可原則的應(yīng)用可以概括：把時間用在真正重要的以概括：把時間用在真正重要的地方，但是首先你

15、必須知道什么地方，但是首先你必須知道什么重要。重要。1716.5.2 six-sigma for software engineeringnthe term “six sigma” is derived from six standard deviations3.4 instances (defects) per million occurrencesimplying an extremely high quality standard. nthe six sigma methodology defines three core steps:ndefine customer requireme

16、nts and deliverables and project goals via well-defined methods of customer communicationnmeasure the existing process and its output to determine current quality performance (collect defect metrics)nanalyze defect metrics and determine the vital few causes.nimprove the process by eliminating the ro

17、ot causes of defects.ncontrol the process to ensure that future work does not reintroduce the causes of defects.1916.6 software reliabilityna simple measure of reliability is mean-time-between-failure (mtbf), where mtbf = mttf + mttrnthe acronyms mttf and mttr are mean-time-to-failure and mean-time-

18、to-repair, respectively.nsoftware availability is the probability that a program is operating according to requirements at a given point in time and is defined asavailability = mttf/(mttf + mttr) x100% 2016.6.2software safetynsoftware safety is a software quality assurance activity that focuses on the identification and assessment of potential hazards that may affect software negatively and cause an entire system to fail. nif hazards can be identified early in the software process, software design features can be specified that will either eliminate or contro