Software Quality Management Concepts

Chapter 3: Software Quality

• This chapter covers software quality fundamentals, management processes, practical considerations, and software quality tools.
• The material includes definitions, costs, models, characteristics, improvement techniques, and safety.

Chapter 3 Contents

• The chapter covers software quality fundamentals, software quality management processes, practical considerations, software quality management techniques, and software quality tools.
• It also describes software engineering culture and ethics, cost of quality, models and quality characteristics, quality improvement, and safety.

ACRONYMS

• CMMI: Capability Maturity Model Integration
• CoSQ: Cost of Software Quality
• COTS: Commercial Off-the-Shelf Software
• FMEA: Failure Mode and Effects Analysis
• FTA: Fault Tree Analysis
• PDCA: Plan-Do-Check-Act
• PDSA: Plan-Do-Study-Act
• QFD: Quality Function Deployment
• SPI: Software Process Improvement
• SQA: Software Quality Assurance
• SQC: Software Quality Control
• SQM: Software Quality Management
• TQM: Total Quality Management
• V&V: Verification and Validation

INTRODUCTION

• Software quality is overloaded. It can refer to desirable characteristics of software, the extent to which a product possesses those characteristics, or the processes, tools, and techniques used to achieve them.
• Different authors and organizations have different definitions of quality.

Breakdown of Topics for Software Quality

• The breakdown shows a hierarchical structure of topics related to software quality.
• Key elements such as software quality fundamentals, management processes, practical considerations and software quality tools are explicitly covered.

1. Software Quality Fundamentals

• Achieving agreement on quality among stakeholders and clearly communicating that agreement to software engineers.
• Software engineers need to understand quality concepts, characteristics, values and their application to software projects.
• Quality attributes are defined in software requirements.

1.1 Software Engineering Culture and Ethics

• Software engineers are expected to be committed to software quality as part of their workplace culture.
• Quality includes understanding the tradeoffs between cost, schedule, and quality.
• A strong software engineering work ethic involves reporting quality information accurately.
• IEEE and ACM codes of ethics play a crucial role.

1.2 Value and Costs of Quality

• Cost of software quality (CoSQ) is a set of measurements derived from the economic assessment of software quality development and maintenance processes.
• Costs associated with poor quality can be categorized as prevention, appraisal, internal failure, and external failure costs.
• Prevention costs involve investments in improving processes, tools, training and other factors.
• Appraisal costs relate to the verification and validation activities.
• Internal failure costs refer to failures discovered before delivery to the customer, and external failure costs refer to those discovered after delivery.
• Software engineers need to consider these costs in their decision making and present quality alternatives.

1.3 Models and Quality Characteristics

• Software quality management and software engineering process quality directly affect the quality of the product.
• Quality improvement involves preventative processes or iterative improvements in processes, defect detection and removal, and the lifecycle of quality improvement.
• Software product and process quality are important factors affecting stakeholders' perception of quality.

1.4. Software Quality Improvement

• Quality improvement involves preventing defects, continually improving processes, and focusing on stakeholders.
• Quality improvement can be derived from processes like Plan-Do-Check-Act (PDCA), and other proven strategies.
• These concepts are linked to quality of the process which directly affects quality of the product perceived by stakeholders.

1.5 Software Safety

• Safety critical systems are those where errors or malfunction may result in harm to people and environment.
• Direct and indirect examples of safety-critical software are mentioned, like flight control computer and applications used to create said computers.
• Strategies involving avoidance, detection, and damage limitations are highlighted as crucial aspects of ensuring safety.
• Standards, like DO-178C, are used to develop safety-critical software.

2. Software Quality Management Processes

• Software quality management encompasses processes ensuring software products meet quality objectives and improve stakeholder satisfaction.
• It includes software quality planning, assurance, control and improvement.
• Quality planning entails defining standards, objectives and estimating efforts and schedules.
• Software quality assurance assesses the adequacy of activities.
• Quality control evaluates project artifacts to ensure compliance with standards.
• Improvement aims to improve process effectiveness and efficiency.

2.1 Software Quality Assurance

• Quality assurance is not just testing; it encompasses product and process aspects.
• Quality assurance plans define activities and tasks for guaranteeing software satisfies user requirements within specified cost, schedule, and risk constraints.
• Various measures, tools and techniques, along with reporting and documentation, form part of software quality assurance plans.

2.2 Verification and Validation

• Verification assists in ensuring that outputs from one phase fulfill the requirements of the preceding phase. Validation ensures the output products fulfill their intended purpose and stakeholder needs.
• Verification and validation processes happen from the beginning of the life cycle.
• A plan for both verification and validation activities is needed to ensure roles and responsibilities are assigned.

2.3 Reviews and Audits

• Reviews and audits are static analysis methods that evaluate artifacts without executing software.
• Different types include management, technical, inspections, and walkthroughs.
• Process assurance audits evaluate plan, schedule and requirements, making sure they meet project objectives.
• Product assurance audits ensure conformance with contracts/standards.

2.3.1 Management Reviews

• Management reviews monitor progress, evaluate plan effectiveness, and assess project status against plans.
• Key factors considered include cost, schedule, scope, and quality.

2.3.2 Technical Reviews

• Technical reviews evaluate software product suitability for use and identify deviations from standards.

2.3.3 Inspections

• Inspections detect and identify product anomalies through predefined rules.
• It involves sampling, peer review, and a moderator to lead.

2.3.4 Walkthroughs

• Walkthroughs are similar to inspections but may be less structured with emphasis on feedback from the participants.
• The author/presenter leads walk through meetings.

2.3.5 Process Assurance and Product Assurance Audits

• Audits assess whether products and processes meet established requirements.
• Roles include lead auditor, auditors, recorder, and initiator.

3. Practical Considerations

• This section clarifies terms used in software quality, such as defect characterization.

3.2 Defect Characterization

• Different definitions of defects, errors, faults, and failures are provided to aid clarity and consistency in software quality analyses.
• Computations, observed, and the true/specified values/conditions are differentiated.
• Defects stem from errors or failures in producing the expected result.