1. 1 Software Engineering: A Practitioner’s Approach, 6/e Chapter 26 Quality Management Software Engineering: A Practitioner’s Approach, 6/e Chapter 26 Quality Management copyright © 1996, 2001, 2005 R.S. Pressman & Associates, Inc. For University Use Only May be reproduced ONLY for student use at the university level when used in conjunction with Software Engineering: A Practitioner's Approach. Any other reproduction or use is expressly prohibited.

2. 2 Quality The American Heritage Dictionary defines quality as The American Heritage Dictionary defines quality as “a characteristic or attribute of something.” “a characteristic or attribute of something.” For software, two kinds of quality may be encountered: For software, two kinds of quality may be encountered: Quality of design encompasses requirements, specifications, and the design of the system. Quality of design encompasses requirements, specifications, and the design of the system. Quality of conformance is an issue focused primarily on implementation. Quality of conformance is an issue focused primarily on implementation. user satisfaction = compliant product + good quality + delivery within budget and schedule user satisfaction = compliant product + good quality + delivery within budget and schedule

3. 3 Software Quality Conformance to explicitly stated functional and performance requirements, explicitly documented development standards, and implicit characteristics that are expected of all professionally developed software.

4. 4 Cost of Quality Prevention costs include Prevention costs include quality planning, formal technical reviews, test equipment and Training quality planning, formal technical reviews, test equipment and Training Appraisal costs include Appraisal costs include In-process and inter-process inspection, equipment calibration and maintenance, and testing In-process and inter-process inspection, equipment calibration and maintenance, and testing Failure costs Failure costs Internal failure costs (before delivery) include Internal failure costs (before delivery) include rework rework repair repair failure mode analysis failure mode analysis External failure costs (after delivery) include External failure costs (after delivery) include complaint resolution complaint resolution product return and replacement product return and replacement help line support help line support warranty work warranty work

5. 5 Software Quality Assurance Formal Technical Reviews Test Planning & Review Measurement Analysis & Reporting Process Definition & Standards The SQA group serves as the customer’s in-house representative.

6. 6 Role of the SQA Group-I Prepares an SQA plan for a project. Prepares an SQA plan for a project. The plan identifies The plan identifies evaluations to be performed evaluations to be performed audits and reviews to be performed audits and reviews to be performed standards that are applicable to the project standards that are applicable to the project procedures for error reporting and tracking procedures for error reporting and tracking documents to be produced by the SQA group documents to be produced by the SQA group amount of feedback provided to the software project team amount of feedback provided to the software project team Participates in the development of the project’s software process description. Participates in the development of the project’s software process description. 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. 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.

7. 7 Role of the SQA Group-II Reviews software engineering activities to verify compliance with the defined software process. Reviews software engineering activities to verify compliance with the defined software process. identifies, documents, and tracks deviations from the process and verifies that corrections have been made. identifies, documents, and tracks deviations from the process and verifies that corrections have been made. Audits designated software work products to verify compliance with those defined as part of the software process. Audits designated software work products to verify compliance with those defined as part of the software process. reviews selected work products; identifies, documents, and tracks deviations; verifies that corrections have been made reviews selected work products; identifies, documents, and tracks deviations; verifies that corrections have been made periodically reports the results of its work to the project manager. periodically reports the results of its work to the project manager. Ensures that deviations in software work and work products are documented and handled according to a documented procedure. Ensures that deviations in software work and work products are documented and handled according to a documented procedure. Records any noncompliance and reports to senior management. Records any noncompliance and reports to senior management. Noncompliance items are tracked until they are resolved. Noncompliance items are tracked until they are resolved.

8. 8 Why SQA Activities Pay Off? cost to find and fix a defect 100 10 log scale 1 Req. Design code test system test field use 0.75 1.00 1.50 3.00 10.00 60.00-100.00

9. 9 Reviews & Inspections... there is no particular reason why your friend and colleague cannot also be your sternest critic. Jerry Weinberg

10. 10 What Are Reviews? a meeting conducted by technical people for technical people a meeting conducted by technical people for technical people a technical assessment of a work product created during the software engineering process a technical assessment of a work product created during the software engineering process a software quality assurance mechanism a software quality assurance mechanism a training ground a training ground Reviews serve to uncover errors and defects that can then be removed at various points during software engineering.

11. 11 The Players review leader producer recorder reviewer standards bearer (SQA) maintenanceoracle user rep

12. 12 Conducting the Review be prepared—evaluate product before the review review the product, not the producer keep your tone mild, ask questions instead of making accusations stick to the review agenda raise issues, don't resolve them avoid discussions of style—stick to technical correctness schedule reviews as project tasks record and report all review results 1. 2. 3. 4. 5. 6. 7. 8. At the end of the review, all attendees of the Formal Technical Reviews must decide whether to (1) accpet the product without further modification, (2) reject the product due to severe errors, or (3) accept the product provisionally.

13. 13 Review Summary A review summary report answers three questions: A review summary report answers three questions: What are reviewed What are reviewed Who reviewed it Who reviewed it What were the findings and conclusions What were the findings and conclusions

14. 14 Review Guidelines Review the product, not the producer Review the product, not the producer Set an agenda and maintain it Set an agenda and maintain it Limit debate and rebuttal Limit debate and rebuttal Enunciate problem areas, but don’t attempt to solve every problem noted Enunciate problem areas, but don’t attempt to solve every problem noted Take written notes Take written notes Limit the number of participants and insist upon advance preparation Limit the number of participants and insist upon advance preparation…

15. 15 Defect Amplification and Removal Figure 26.2 Figure 26.2 Errors passed through Errors passed through Amplified errors 1: x Amplified errors 1: x Newly generated errors Newly generated errors Figure 26.3 Figure 26.3 no reviews are conducted Figure 26.4 Figure 26.4 reviews are conducted (preliminary design, detail design, code)

16. 16 Sample-Driven Reviews (SDRs) SDRs attempt to quantify those work products that are primary targets for full FTRs. SDRs attempt to quantify those work products that are primary targets for full FTRs. To accomplish this … Inspect a fraction a i of each software work product, Record the number of faults f i found within a i. Inspect a fraction a i of each software work product, Record the number of faults f i found within a i. Develop a gross estimate of the number of faults within work product i by multiplying f i by 1/a i. Develop a gross estimate of the number of faults within work product i by multiplying f i by 1/a i. Sort the work products in descending order according to the gross estimate of the number of faults in each. Sort the work products in descending order according to the gross estimate of the number of faults in each. Focus available review resources on those work products that have the highest estimated number of faults. Focus available review resources on those work products that have the highest estimated number of faults.

17. 17 Metrics Derived from Reviews inspection time per page of documentation inspection time per KLOC or FP errors uncovered per reviewer hour errors uncovered per preparation hour errors uncovered per SE task (e.g., design) number of minor errors (e.g., typos) number of errors found during preparation number of major errors (e.g., nonconformance to req.) (e.g., nonconformance to req.) inspection effort per KLOC or FP

18. 18 Statistical SQA Product & Process measurement... an understanding of how to improve quality... Collect information on all defects Find the causes of the defects Move to provide fixes for the process

19. 19 An Example Figure 26.5 Figure 26.5 The causes of errors, number of errors be found, percentage vital causes according to total percentage: IES, MCC, EDR vital causes according to serious percentage: IES, EDR, EDL, PLT

20. 20 Six-Sigma for Software Engineering The term “six sigma” is derived from six standard deviations—3.4 instances (defects) per million occurrences—implying an extremely high quality standard. The term “six sigma” is derived from six standard deviations—3.4 instances (defects) per million occurrences—implying an extremely high quality standard. The Six Sigma methodology defines three core steps: The Six Sigma methodology defines three core steps: Define customer requirements and deliverables and project goals via well- defined methods of customer communication Define customer requirements and deliverables and project goals via well- defined methods of customer communication Measure the existing process and its output to determine current quality performance (collect defect metrics) Measure the existing process and its output to determine current quality performance (collect defect metrics) Analyze defect metrics and determine the vital few causes. Analyze defect metrics and determine the vital few causes. Improve the process by eliminating the root causes of defects. Improve the process by eliminating the root causes of defects. Control the process to ensure that future work does not reintroduce the causes of defects.

21. 21 Software Reliability A simple measure of reliability is mean-time-between- failure (MTBF), where A simple measure of reliability is mean-time-between- failure (MTBF), where MTBF = MTTF + MTTR Where the acronyms MTTF and MTTR are mean-time- to-failure and mean-time-to-repair, respectively. Running Repairing failure Running Repairing failure MTBF

22. 22 Software Availability Software availability is the probability that a program is operating according to requirements at a given point in time and is defined as Software availability is the probability that a program is operating according to requirements at a given point in time and is defined as Availability = [MTTF/(MTTF + MTTR)] x 100%

23. 23 Software Safety Software 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. Software 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. If hazards can be identified early in the software process, software design features can be specified that will either eliminate or control potential hazards. If hazards can be identified early in the software process, software design features can be specified that will either eliminate or control potential hazards.

24. 24 ISO 9001:2000 Standard ISO 9001:2000 is the quality assurance standard that applies to software engineering. ISO 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 standard contains 20 requirements that must be present for an effective quality assurance system. The requirements delineated by ISO 9001:2000 address topics such as The requirements delineated by ISO 9001:2000 address topics such as management responsibility, quality system, contract review, design control, document and data control, product identification and traceability, process control, inspection and testing, corrective and preventive action, control of quality records, internal quality audits, training, servicing, and statistical techniques. management responsibility, quality system, contract review, design control, document and data control, product identification and traceability, process control, inspection and testing, corrective and preventive action, control of quality records, internal quality audits, training, servicing, and statistical techniques.