軟件工程-實(shí)踐者的研究方法chapter_13

1、these slides are designed to accompany software engineering: a practitioners approach, 7/e (mcgraw-hill 2009). slides copyright 2009 by roger pressman.1chapter 13nsoftware quality assuranceslide set to accompanysoftware engineering: a practitioners approach, 7/e by roger s. pressmanslides copyright

2、1996, 2001, 2005, 2009 by roger s. pressmanfor non-profit educational use onlymay be reproduced only for student use at the university level when used in conjunction with software engineering: a practitioners approach, 7/e. any other reproduction or use is prohibited without the express written perm

3、ission of the author.all copyright information must appear if these slides are posted on a website for student use.these slides are designed to accompany software engineering: a practitioners approach, 7/e (mcgraw-hill 2009). slides copyright 2009 by roger pressman.2comment on qualitynphil crosby on

4、ce 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 certain conditions, of course.) neveryone feels they understand it. (even though they

5、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 caused by other people. (if only they would take the time to do things right.)these sli

6、des are designed to accompany software engineering: a practitioners approach, 7/e (mcgraw-hill 2009). slides copyright 2009 by roger pressman.3elements of sqanstandards nreviews and audits ntestingnerror/defect collection and analysis nchange management neducation nvendor management nsecurity manage

7、ment nsafety nrisk management these slides are designed to accompany software engineering: a practitioners approach, 7/e (mcgraw-hill 2009). slides copyright 2009 by roger pressman.4role of the sqa group-inprepares an sqa plan for a project. nthe plan identifiesevaluations to be performedaudits and

8、reviews to be performedstandards that are applicable to the projectprocedures for error reporting and trackingdocuments to be produced by the sqa groupamount of feedback provided to the software project teamnparticipates in the development of the projects software process description. n the sqa grou

9、p 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.these slides are designed to accompany software engineering: a practitioners approach, 7/e (mcgraw-hil

10、l 2009). slides copyright 2009 by roger pressman.5role of the sqa group-iinreviews 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 s

11、oftware work products to verify compliance with those defined as part of the software 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 de

12、viations in software work and work products are documented and handled according to a documented procedure.nrecords any noncompliance and reports to senior management.nnoncompliance items are tracked until they are resolved.these slides are designed to accompany software engineering: a practitioners

13、 approach, 7/e (mcgraw-hill 2009). slides copyright 2009 by roger pressman.6sqa goals (see figure 16.1)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

14、element of the design model should be assessed by the software team to ensure that it exhibits 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 exhibi

15、t characteristics that will facilitate maintainability.nquality control effectiveness. a software team should apply limited resources in a way that has the highest likelihood of achieving a high quality result.these slides are designed to accompany software engineering: a practitioners approach, 7/e

16、 (mcgraw-hill 2009). slides copyright 2009 by roger pressman.7statistical sqameasurement. an understanding of how to improve quality .collect information on all defectsfind the causes of the defectsmove to provide fixes for the processthese slides are designed to accompany software engineering: a pr

17、actitioners approach, 7/e (mcgraw-hill 2009). slides copyright 2009 by roger pressman.8statistical sqaninformation about software errors and defects is collected and categorized.nan attempt is made to trace each error and defect to its underlying cause (e.g., non-conformance to specifications, desig

18、n error, violation of standards, poor communication with the customer).nusing the pareto principle (80 percent of the defects can be traced to 20 percent of all possible causes), isolate the 20 percent (the vital few).nonce the vital few causes have been identified, move to correct the problems that

19、 have caused the errors and defects.these slides are designed to accompany software engineering: a practitioners approach, 7/e (mcgraw-hill 2009). slides copyright 2009 by roger pressman.9six-sigma for software engineeringnthe term “six sigma” is derived from six standard deviations3.4 instances (de

20、fects) per million occurrencesimplying an extremely high quality standard. nthe six sigma methodology defines three core steps:ndefine customer requirements and deliverables and project goals via well-defined methods of customer communicationnmeasure the existing process and its output to determine

21、current quality performance (collect defect metrics)nanalyze defect metrics and determine the vital few causes.nimprove the process by eliminating the root causes of defects.ncontrol the process to ensure that future work does not reintroduce the causes of defects.these slides are designed to accomp

22、any software engineering: a practitioners approach, 7/e (mcgraw-hill 2009). slides copyright 2009 by roger pressman.10software 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-t

23、o-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) x 100% these slides are designed to accompany software engineering: a practitioners approach, 7/e (mcgraw

24、-hill 2009). slides copyright 2009 by roger pressman.11software 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 tha