Software Engineering - Software Quality.ppt
- 2. 2 Plan of the Talk Introduction to Quality Engineering. Quality control and Quality Assurance ISO 9000 SEI CMM Summary
- 3. 3 Introduction Traditional definition of quality: • Fitness of purpose: A quality product does exactly what the users want it to do.
- 4. 4 Fitness of Purpose Fitness of purpose for software products: Satisfaction of the requirements specified in SRS document.
- 5. 5 Fitness of Purpose A satisfactory definition of quality for many products: • A car, a table fan, a food mixer, microwave oven, etc. But, not satisfactory for software products. • Why?
- 6. 6 Quality for Software Products Consider a software product: • Functionally correct: Performs all functions as specified in the SRS document. • But, has an almost unusable user interface. Cannot be considered as a quality product.
- 7. 7 Quality for Software Products Consider another example: • A product which does everything that users want. • But has an almost incomprehensible and unmaintainable code. • Will you call it a quality product?
- 8. 8 Modern View of Quality Several quality factors are associated with a software product : • Correctness • Reliability • Efficiency (includes efficiency of resource utilization) • Portability • Usability • Reusability • Maintainability
- 9. 9 Correctness A software product is correct: • If different requirements as specified in the SRS document have been correctly implemented. • Results are accurate.
- 10. 10 Portability A software product is said to be portable: • If it can be easily made to work In different operating systems. In different machines, With other software products, etc.
- 11. 11 Reusability A software product has good reusability: • If different modules of the product can easily be reused to develop new products.
- 12. 12 Usability A software product has good usability: • If different categories of users (i.e. both expert and novice users) can easily invoke the functions of the product.
- 13. 13 Maintainability A software product is maintainable: • If errors can be easily corrected as and when they show up, • New functions can be easily added to the product, • Functionalities of the product can be easily modified.
- 14. 14 Software Quality Management System Quality management system (or quality system): • Principal methodology used by organizations to ensure that the products have desired quality.
- 15. 15 Quality System A quality system consists of the following: • Managerial Structure • Individual Responsibilities. Responsibility of the organization as a whole.
- 16. 16 Quality System Every quality conscious organization has an independent quality department: • Performs several quality system activities. • Needs support of top management. • Without support at a high level in a company: Many employees may not take the quality system seriously.
- 17. 17 Quality System Activities Auditing of projects Development of: • standards, procedures, and guidelines. Production of reports for the top management: • Summarizing the effectiveness of the quality system in the organization. Review of the quality system itself.
- 18. 18 Quality System A good quality system must be well documented. • Without a properly documented quality system, Application of quality procedures become ad hoc, Results in large variations in the quality of the products delivered.
- 19. 19 Quality System An undocumented quality system: • Sends clear messages to the staff about the attitude of the organization towards quality assurance. International standards such as ISO 9000 provide: • Guidance on how to organize a quality system.
- 20. 20 Evolution of Quality Systems Quality systems have evolved: • Over the last six decades. Prior to World War II: • Accepted way to produce quality products: Inspect the finished products Eliminate defective products.
- 21. 21 Evolution of Quality Systems Since World war II, • Quality systems of organizations have undergone: Four stages of evolution. Many advances came from Japanese: • Helped resurrect Japanese economy.
- 23. 23 Evolution of Quality Systems Initial product inspection method: • Gave way to quality control (QC). Quality control: • Not only detect the defective products and eliminate them • But also determine the causes behind the defects.
- 24. 24 Quality Control (QC) Quality control aims at correcting the causes of errors: • Not just rejecting defective products. Statistical quality control (SQC): • Quality of the output of the process is inferred using statistical methods. • In stead of inspection or testing of all products.
- 25. 25 Quality Control (QC) The next breakthrough: • Development of quality assurance principles.
- 26. 26 Quality Assurance Basic premise of modern quality assurance: • If an organization's processes are good and are followed rigorously: The products are bound to be of good quality.
- 27. 27 Quality Assurance All modern quality paradigms include: • Guidance for recognizing, defining, analyzing, and improving the production process.
- 28. 28 Total Quality Management (TQM) TQM advocates: • Continuous process improvements through process measurements.
- 29. 29 Business Process Reengineering BPR:A term related to TQM. Process reengineering goes a step further than quality assurance: • Aims at continuous process improvement.
- 30. 30 Business Process Reengineering TQM focuses on reengineering of the software process. Whereas BPR aims at reengineering the way business is carried out in any organization: Not just software development.
- 31. 31 Total Quality Management (TQM) TQM goes beyond documenting processes • Optimizes them through redesign. Over the years the quality paradigm has shifted: • From product assurance to process assurance.
- 32. 32 Implies introducing process changes to improve: • Product quality • Reduce costs • Accelerate schedules. Most process improvement work so far has focused on defect reduction. Process Improvement
- 33. 33 Process Attributes Process characteristic Description Under st andability To what extent is the process explicit ly defined and how ea sy is it t o under st and t heprocess definition? Visibility Do the process activities culminate in clear result s so t hat the progress oftheprocess is exter nally visible? Supportability To what extent can CASE tools be used t o support the process activities? Acce pta bility Is the defined process acce pta ble t o and usable by the enginee rs responsiblefor p roducing th e s oftwareproduct? Reliability Is t he processdesigned in such a way thatprocess errorsare avoided or trapped b eforethey r esultin producterrors ? Robustness Can theprocesscont inuein spiteofunexpect ed problems? Mainta inability Can the processevolve to re flect changing organisat ional re quirements oridentified p rocess improvements ? Rapidity How fast can th e process of delivering a syste m from a given specification becompleted?
- 35. 35 Process measurement • Attributes of the process are measured. • Form a baseline for assessing improvements. Process analysis • The process is assessed and bottlenecks and weaknesses are identified. Process change • Changes to the process that have been identified during the analysis are introduced. Process Improvement Stages
- 36. 36 A good process is usually required to produce a good product. For manufactured goods, process is the principal quality determinant. For design-based activity, other factors are also involved: • For example, the capabilities of the designers. Process and Product Quality