What is Software Quality?

1. What is Software Quality?

2. Popular View of Quality • Quality is an intangible trait. • “I know it when I see it.” • I.e., it is interpreted in different ways. • Therefore, it cannot be controlled, managed, measured. • Often connotes luxury, class, and/or taste. (A Cadillac is a quality car and a Chevrolet is not.)

3. Professional View of Quality • Crosby (1979) describes quality as “conformance to requirements”. • Nonconformances are defects – the absence of quality. • If a car conforms to all its requirements, it is a quality car regardless of whether it is a Cadillac or a Chevrolet. • Juran and Gryna (1970) describe it as “fitness for use”. • Takes customers’ requirements and expections into account.

4. The Role of the Customer • From the Customer’s standpoint, quality is the perceived value of the product – price, performance, reliability, etc. • This implies the customer’s requirements and expectations must be fully understood. • In addition to adherence to requirements, customer satisfaction is the ultimate validation of quality.

5. Big Q and Small q • The definition quality consists of two levels. • The intrinsic product quality – the product’s defect rate and reliability – “small q” • The broader view including product quality, process quality, and customer satisfaction – “big Q” • This forms a closed-loop cycle: customer wants and needs  requirements and specifications  products designed, developed and built according to the requirements with constant attention to process improvement  excellent product quality and support  total customer satisfaction.

6. Software Quality • Narrow definition: lack of bugs in the product. • Broader definition: • Conformance to requirements: measured by defect rate and reliability • Customer satisfaction: measured by surveys • IBM monitors satisfaction in levels of CUPRIMDSO • HP focuses on FURPS

7. Updated Definition of Quality • Software quality is conformance to customers’ requirements.

8. Interrelationships of Software Quality Attributes

9. Total Quality Management • Total Quality Management (TQM) was coined in 1985 by the Naval Air Systems Command to describe its approach to quality improvement. • It represents a style of management that links quality to customer satisfaction. • Examples include: • The Malcolm Baldrige National Quality Award (MBNQA) • ISO 9000 • HP’s Total Quality Control (TQC) • Motorola’s Six Sigma Strategy • IBM’s Market Driven Quality

10. Total Quality Management (Cont’d) • Key elements of TQM • Customer focus • Process improvement • Human side of quality • Measurement and analysis • Organizational frameworks: • Plan-Do-Check-Act – Deming (1986) • Quality Improvement Paradigm/Experience Factory Organization – Basili (1985) • Software Engineering Institute (SEI) Capability Maturity Model (CMM) – Humphrey (1989) • Lean Enterprise Management – Womack (1990)

11. Total Quality Management (Cont’d)

12. Plan-Do-Check-Act • Based on a feedback cycle for optimizing a single process • Uses feedback loops and statistical quality control to experiment with methods for improvement and to build predictive models. • Based on assumption that a process is repeated multiple times so models can be built that allow predictions.

13. Quality Improvement Paradigm/Experience Factory Organization • Aim is to continually improve the organization based on its evolving goals and an assessment of status relative to those goals. • The six fundamental steps are: • Characterize the project and its environment • Set the goals • Choose the appropriate processes • Execute the processes • Analyze the data • Package the experience for reuse

14. The SEI Capability Maturity Model • A staged process improvement based on assessment of key process areas until level 5 (a state of continuous process improvement) is reached • A five level process maturity model is defined based on repeated assessments of capabilities in key process areas • The basic idea is that there are key process areas and attending to them will improve software development

15. Lean Enterprise Management • Based on the principle of concentration of production on “value-added” activities • Goal is to build software with the minimum necessary set of activities and then to tailor the process to the product’s requirements.