©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 1 Quality Management

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 2 What is quality? l Quality, simplistically, means that a product should meet its specification. l This is problematical for software systems There is a tension between customer quality requirements (efficiency, reliability, etc.) and developer quality requirements (maintainability, reusability, etc.); Some quality requirements are difficult to specify in an unambiguous way; Software specifications are usually incomplete and often inconsistent. Maintainability requirements can have impact on the system designed and the implementation. Easy to maintain is to bring future expectations into the system. But what will the future bring?

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 3 The quality compromise l We cannot wait for specifications to improve before paying attention to quality management. l We must put quality management procedures into place to improve quality in spite of imperfect specification. l Can you ensure quality by designing standards or are you just ensuring bureaucracy ?

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 4 Scope of quality management l Quality management is particularly important for large, complex systems. The quality documentation is a record of progress and supports continuity of development as the development team changes. l For smaller systems, quality management needs less documentation and should focus on establishing a quality culture.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 5 Quality management activities l Quality assurance Establish organisational procedures and standards for quality. l Quality planning Select applicable procedures and standards for a particular project and modify these as required. l Quality control Ensure that procedures and standards are followed by the software development team. l Quality management should be separate from project management to ensure independence.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 6 Quality management and software development

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 7 l The quality of a developed product is influenced by the quality of the production process. l This is important in software development as some product quality attributes are hard to assess. l However, there is a very complex and poorly understood relationship between software processes and product quality. Process and product quality

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 8 Process-based quality

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 9 l Define process standards such as how reviews should be conducted, configuration management, etc. l Monitor the development process to ensure that standards are being followed. l Report on the process to project management and software procurer. l Don’t use inappropriate practices simply because standards have been established. Practical process quality

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 10 l Encapsulation of best practice- avoids repetition of past mistakes. l They are a framework for quality assurance processes - they involve checking compliance to standards. l They provide continuity - new staff can understand the organisation by understanding the standards that are used. Importance of standards

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 11 Product and process standards

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 12 Problems with standards l They may not be seen as relevant and up-to- date by software engineers. l They often involve too much bureaucratic form filling. l If they are unsupported by software tools, tedious manual work is often involved to maintain the documentation associated with the standards.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 13 ISO 9000 l ISO standard is very general and abstract l Is to be interpreted by the branch in which it is to be implemented. l Many branches have made special standards based on ISO 9000, in which the branch’s interpretation is stated.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 14 ISO 9000 l An international set of standards for quality management. l Applicable to a range of organisations from manufacturing to service industries. l ISO 9001 applicable to organisations which design, develop and maintain products. l ISO 9001 is a generic model of the quality process that must be instantiated for each organisation using the standard.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 15 ISO 9001

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 16 ISO 9000 certification l Quality standards and procedures should be documented in an organisational quality manual. l An external body may certify that an organisation’s quality manual conforms to ISO 9000 standards. l Some customers require suppliers to be ISO 9000 certified although the need for flexibility here is increasingly recognised.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 17 ISO 9000 certification l Quality standards and procedures should be documented in an organisational quality manual. l An external body may certify that an organisation’s quality manual conforms to ISO 9000 standards. l Some customers require suppliers to be ISO 9000 certified although the need for flexibility here is increasingly recognised.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 18 Documentation process

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 19 Document standards l Document identification standards How documents are uniquely identified. l Document structure standards Standard structure for project documents. l Document presentation standards Define fonts and styles, use of logos, etc. l Document update standards Define how changes from previous versions are reflected in a document.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 20 Quality plans l Quality plan structure Product introduction; Product plans; Process descriptions; Quality goals; Risks and risk management. l Quality plans should be short, succinct documents If they are too long, no-one will read them.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 21 Software quality attributes

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 22 Quality control l This involves checking the software development process to ensure that procedures and standards are being followed. l There are two approaches to quality control Quality reviews; Automated software assessment and software measurement.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 23 Types of review

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 24 l Any type of measurement which relates to a software system, process or related documentation Lines of code in a program, the Fog index, number of person-days required to develop a component. l Allow the software and the software process to be quantified. l May be used to predict product attributes or to control the software process. l Product metrics can be used for general predictions or to identify anomalous components. Software metric

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 25 Predictor and control metrics

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 26 Internal and external attributes

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 27 Software product metrics

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 27 Slide 28 Object-oriented metrics