Quality Concept

1. Quality Concept Computer Science Department, Faculty Of Science Prince of Songkhla University Apirada Thadadech

2. Content • How is measures quality? • Cost of quality • The quality triangle • Type of software quality Quality Concept

3. How is measures quality? • Quality is frequently associated with some measure of : • Goodness, • Excellence • Luxury Quality Concept

4. How is measures quality?(next) There are 4 other, equally valid perspectives: • The user’ s perspective : Product is fitness for requirements. • The manufacturer’s : how well a product conform to specification. • The product perspective: measurable attributes of a product. • The value-based perspective: what a customer is willing to pay for quality. Quality Concept

5. Table Of Quality Measures Quality Concept

6. Cost of quality There are 2 major elements • The cost of quality improvement: associated with activities (Table 1) • Defect prevention • Appraisal • The cost of failure : fails to meet its quality requirements (Table 2) • Internal failure – prior to transfer of ownership to the customer • External failure– after transfer of ownership to the customer Quality Concept

7. Table 1 Typical quality improvement costs Quality Concept

8. Table 2 Typical quality failure costs Quality Concept

9. Cost of Quality Curve Cost 0% Quality 100% Quality Concept

10. The quality triangle • Products can suffer from poor quality in number of different ways: • User’s view • Product’s view • Manufacturer’s view Quality Concept

11. The Quality Triangle Product View product Gap User Requirements User’s View Specification Manufacturer’s View Quality Concept

12. User Requirement – Specification gap • Misunderstood requirements • Ignored requirements • Missing requirements • Outdated requirements • Unneeded requirements Quality Concept

13. Specification – Product Gap • Wrong interpretation of requirement cause of ambiguity in specification • Requirements identified after development commented • Changes to specified requirements identified after development commented • Features added by the developers follow technical • Requirements ignored by the developers cause of they were too difficult to implement Quality Concept

14. Product – User Requirement Gap • The gap is directly dependent on 2 side of triangle • If two sides are short, then this gap will be small • If two sides are long, then this gap will be large Quality Concept

15. The Quality Triangle If the quality better aligned the triangle will become smaller If all view are perfectly aligned, it will be represented by a single dot. Product Specification UserRequirements Quality Concept

16. Quality triangle shapes Quality Concept

17. Quality triangle shapes Quality Concept

18. Software Product Measurement • In Table list a number of the more popular measures of Software Product quality • The ISO 9126 Standard for Software Product Quality Quality Concept

19. Quality Concept

20. Software Quality • External Quality • Internal Quality • Quality in Use Quality Concept

21. External Quality Internal Quality Quality in Use The Quality Triangle product Specification User Requirements Quality Concept