1. Chapter 7.2

2. Continuing:  Factors affecting intensity of SQA activities  Verification, validation and qualification  Development and quality plans for small and for internal projects  A model for SQA defect removal effectiveness and cost Lesson Outlines

3. Factors affecting Intensity of SQA Activities SQA Activities are linked to the completion of a project phase –Requirements, design, etc. The SQA activities need to be integrated into the development plan that implements one or more software development models, such as the waterfall, prototyping, spiral, …

4. Factors affecting Intensity of SQA Activities SQA planners need to determine –A list of SQA activities needed for the project –And then for each activity, they need to decide on Timing Type of QA activity to be applied Who performs the activity and resources required. –Important to note that many participate in SQA activities »Development team »Department staff members »Independent bodies Resources required for the removal of defects and introduction of changes.

5. Factors affecting Intensity of SQA Activities Sad testimony that few want to allocate the necessary time for SQA activities. –This means time for SQA activities and then time for subsequent removal of defects. –Often, there is no time for follow-on work!! Activities are not simply ranked in and absorbed! So, time for SQA activities and defect correction actions needs to be examined.

6. Factors Affecting the Required Intensity of QA Activity Project Factors –Magnitude of the project – how big is it? –Technical complexity and difficulty –Extent of reusable software components – a real factor –Severity of failure outcomes if project fails – essential! Team Factors –Professional qualifications of the team members –Team acquaintance w/ project and experience in the area –Availability of staff members who can professionally support the team, and –Percentage of new staff members in the team.

7. Example A software development team has planned the quality assurance activities for its new consumer club project. The team estimates that about seven man-months need to be invested by the two team members assigned to the project, whose duration is estimated at four months. It is estimated that a reusable components library can supply 90% of the project software. Three quality assurance activities were planned by the project leader. The quality assurance activities and their duration are listed in Table 7.1.

8. Table 7.1 The main considerations affecting this plan are: ■ Degree of team acquaintance with the subject ■ High percentage of software reuse ■ Size of the project (in this case, medium) ■ Severity of failure results if the project fails.

9. Verification – The process of evaluating a system or component to determine whether the products of a given development phase satisfy the conditions imposed at the start of that phase Validation - The process of evaluating a system or component during or at the end of the development process to determine whether it satisfies specified requirements Qualification - The process used to determine whether a system or component is suitable for operational use Verification, Validation, and Qualification Three aspects of Quality Assurance for Software Products:

10. More on VV and Q Verification looks at the consistency of the products being developed with products developed in previous phases. Developers verify as we go. Validation is a customer thing – customers validate the outputs, etc. Validate against their original requirements. Necessary for customer satisfaction. Qualification focuses on operational aspects – maintenance is the main issue. Planners need to determine which of all these need to be examined in each QA activity.

11. The model addresses two quantitative aspects of the SQA planning addressing several defect detection activities: 1.Want to study the SQA plan’s total effectiveness in removing project defects, and (فعالية) 2.The total costs of removal of project defects (تكلفة) Note again that SQA activities must be integrated within the project’s development plan. Model for SQA defect removal effectiveness and cost

12. Model for Defect Removal The data: Model based on three types of data: Defect origin distribution in which phase did the defects occur Defect removal effectiveness, and how effective are we at removal of defects? Cost of defect removal. how much does it cost per defect per phase!!!

13. Defect Origin Distribution Very consistent over many years: Distribution of Defects: PhasesAverage –Requirements Specs.15% –Design35% –Coding / integration40% –Documentation10%

14. Defect Removal Effectiveness Generally speaking, the percentage of removed defects is lower than the percentage of detected defects, because some corrections are ineffective or inadequate. We simply miss some!! Others are undetected and uncorrected and passed on to successive development phases. Lingering defects (العيوب العالقة) coupled with introduced defects in current development phase add up!!! For discussion purposes, we will assume the filtering effectiveness of accumulated defects of each quality assurance activity is not less than 40%, that is, each activity removes at least 40% of the incoming defects.

15. Defect Removal Effectiveness Removal effectiveness –QA ActivityAverage defect filtering effectiveness rate requirements specs review50% design inspection 60% design review50% code inspections65% unit test50% Unit test > code review30% integration test50% system tests / acceptance 50% documentation review50%

16. Cost Removal Removal of defects differs very significantly by development phase. Cost are MUCH greater in later development phases. Note: In general, defect removal data is not commonly available. Most agree with the data based on key studies. (next slide)

17. Defect removal phaseDefect removal effectiveness Average relative defect removal cost {cost unit} Defect origination phase ReqDesUniIntDoc Requirement specification (Req)50% 1 --- Design (Des)50% 2.5 1--- Unit coding (Uni)50% 6.5 2.61--- Integration (Int) System documentation (Doc) 50% 16 6.4 2.5 1 1 System testing / Acceptance testing (Sys) 50% 40 166.22.51 Opertion by customer (after release) 100% 110 44176.92.5 Defects removal effectiveness for quality assurance plans

18. The Model Our Model is based on following assumptions: Development process is linear, sequential following waterfall model There is a number of new defects introduced each phase Review and test software quality assurance activities serve as filters, removing a percentage of defects and letting the rest pass to next development phase as we saw three slides back. At each phase, incoming defects are the sum of those not removed plus new defects in current phase Cost of defect removal is calculated for each SQA activity by multiplying the number of defects removed by the relative cost of removing a defect Remaining defects are passed to the customer. (this is the heaviest cost for defect removal)

19. Model - parameters The models we show use these parameters: –POD – Phase originated defects (slid 13) –PD – Passed defects (from former phases) –%FE - % of filtering effectiveness (slid 15) –RD – Removed defects –CDR – Cost of defect removal (slid 17) –TRC – Total Removal Costs

20. First Model (standard) This model applies a standard quality assurance plan (standard defects filtering system) composed of QA activities, that is, ‘filters’ we have: QA activityremoval effectiveness Cost of removing defect 1.Requirements Spec review 50%1 2.Design Review50%2.5 3.Unit Test50%6.5 4.Integration tests50%16 5.Documentation Review50% 16 6.System Test50% 40 7.Operation Phase100% 110

21. Using the standard quality assurance plan’s quality assurance activities on previous slide, a process-oriented illustration of the standard QA plan model follows:

22. POD – phase originated defects PD – passed defects %FE – percent filtering RD – removed defects CDR - Cost of removing defects TRC - Total Cost of Defect Removal

23. Costs of Defect Removal But we can do better using a comprehensive quality assurance plan with more activities, and hence better filtering. The comprehensive quality assurance plan (comprehensive defects filtering system) accomplishes the following: 1. Adds two quality assurance activities so that the two are performed in the design phase as well as in the coding phase –We have a Design Inspection and a Design Review vice Design, and –Code Inspections and unit test vice simple Unit Test 2. Improves the ‘filtering’ effectiveness of other quality assurance activities.

24. Comprehensive Quality Assurance Plan: POD – phase originated defects PD – passed defects %FE – percent filtering RD – removed defects CDR - Cost of removing defects TRC - Total Cost of Defect Removal Design Inspect and Design Review Code inspection precedes unit test 2.6 6.6 6.5 10.5 and 6.3 12.3 and 4.9

25. Comprehensive Plan Conclusions: The standard plan successfully removes 57.6% of the defects in requirements and design compared to 90.2% in the comprehensive plan before coding begins. –Results from more intensive defect-removal efforts. The comprehensive plan as a whole is much more economical than the standard plan as it saves 41% of the total resources investing in defect removal, compared with the standard plan Compared to the standard plan, the comprehensive plan makes a greater contribution to customer satisfaction by drastically reducing the rate of defects detected during regular operations: 6.9% to 2.6%

26. Conclusion So, in general, the quantitative results of the comparison comply nicely with the SQA approach. Additional investments in QA activities yield substantial savings in defect removal costs.

27. Homework Individually, you are to answer the following questions and send them to me via Blackboard Assignment. Questions: 7.6 and 7.7

28. Discussion Forum Team 3: Here are your primary questions: These are the ones for you to provide for class discussion with your team being the primary participants Questions: 7.2, 7.5, 7.4