软件工程英文教学课件：Ch16 Software Quality Assurance

1、1Chapter 16Software Quality AssuranceSoftware Engineering: A Practitioners Approach, 7/e by Roger S. Pressman2Comment on QualityThe 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:Everyb

2、ody is for it. (Under certain conditions) Everyone feels they understand it. (Even though they wouldnt want to explain it.) Most people feel that problems in these areas are caused by other people. (If only they would take the time to do things right.)3Elements of SQA(SQA-Software Quality Assurance)

3、Standards ReviewsTestingError/defect analysis Change management Security management Risk management 4Role of SQA GroupPrepares an SQA plan for a project. The plan identifies:evaluations to be performedreviews to be performedstandards that are applicable to the projectprocedures for error reporting a

4、nd trackingdocuments to be produced by SQA groupfeedback provided to software project teamParticipates in the development of the projects software process description. The SQA group reviews the process description for compliance(服从) with organizational policy, internal software standards, externally

5、 standards (e.g. ISO-9001), and other parts of software project plan.Reviews software engineering activities to verify compliance with the defined software process. Ensures that deviations(偏离) in software work and work products are documented and handled according to a documented procedure.5SQA Goal

6、sRequirements quality. The correctness, completeness, and consistency of the requirements model will have a strong influence on the quality of all work products. Design quality. Every element of the design model should be assessed by the software team to ensure that it exhibits high quality and that

7、 the design itself conforms to requirements.Code quality. Source code and related work products must conform to local coding standards and exhibit characteristics that will facilitate maintainability.Quality control effectiveness. A software team should apply limited resources in a way that has the

8、highest likelihood of achieving a high quality result.6Statistical SQAInformation about software errors and defects is collected and categorized(第一步：故障分类)An attempt is made to trace each error and defect to its underlying(潜在) cause (e.g., non-conformance to specifications, design error, violation(违反

9、) of standards, poor communication with the customer)(第二步：原因分析)Using 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)(第三步：原因确认)Once the vital few causes have been identified, move to correct the problems that

10、have caused the errors and defects(第四步：故障排除)7Software Reliability and AvailabilityA simple measure of reliability is mean-time-between-failure (MTBF平均故障间隔时间), where MTBF = MTTF + MTTRMTTF and MTTR are mean-time-to-failure(平均无故障时间)and mean-time-to-repair(平均修复时间) respectively.Software availability(软件可

11、用性) 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% 8ISO 9001:2000 StandardISO 9001:2000 is the quality assurance standard that applies to software engineering. The standard contains 20 requirements that must be present for an effective quality assurance system. The requirements delineated(描绘) by ISO 9001:2000 address topics such as management responsibility, quality system, contract review, design control, document and data control, product identif