Software Quality Management
The notion of "quality" is not as simple as it may seem. For any engineered product, many desired qualities are relevant to a particular project. The section explains software quality fundamentals, including the main SQM processes: quality assurance, verification, validation, review, and audit. Software quality refers to the delivered product of a software development project, but that quality depends on the quality of the "upstream" products from which it was derived, including requirements, design, construction, and the software quality activities that support it during the development, namely, validation, verification, testing, and measurement. Software quality terminology is numerous, informal, formal, and often ambiguous, with multiple categorizations (internal, external, operational, and feature quality). All of this makes software quality interesting to study.
From a domain perspective, software quality applies to both the problem application domain and the solution domains. It applies to all software development activities and all software products. It is interdisciplinary in that it is a topic in management, software engineering, mathematics, statistics, measurement, and more. It intersects the generic categories of human, software, and hardware and refers to the evolving relationships of these generic types. This last observation hints at the next stage in the evolution of computing technology.
Software quality is a major driving factor for computing technology evolution, which is increasing our capabilities to solve complex problems better, faster, on a larger scale, and with more automation. Generally, the problem domain gets smaller as the solution domain gets larger. The solution domain gets larger as hardware and software support becomes automated. More automation often begins with new abstractions we make in the problem domain, resulting in new relationships between hardware and software, eventually manifesting as automated support tools. We give names to these tools: "cloud computing", big databases, programming languages (front-end, network, back-end, and so on), and AI (natural language translation, image recognition, and machine learning). Indeed, software quality is very interesting.
Software Quality Fundamentals
Value and Costs of Quality
The notion of "quality" is not as simple as it may seem. For any engineered product, there are many desired qualities relevant to a particular perspective of the product, to be discussed and determined at the time that the product requirements are set down. Quality characteristics may be required or not, or may be required to a greater or lesser degree, and trade-offs may be made among them.
The cost of quality can be differentiated into prevention cost, appraisal cost, internal failure cost, and external failure cost.
A motivation behind a software project is the desire to create software that has value, and this value may or may not be quantified as a cost. The customer will have some maximum cost in mind, in return for which it is expected that the basic purpose of the software will be fulfilled. The customer may also have some expectation as to the quality of the software. Sometimes customers may not have thought through the quality issues or their related costs. Is the characteristic merely decorative, or is it essential to the software? If the answer lies somewhere in between, as is almost always the case, it is a matter of making the customer a part of the decision process and fully aware of both costs and benefits. Ideally, most of these decisions will be made in the software requirements process, but these issues may arise throughout the software life cycle. There is no definite rule as to how these decisions should be made, but the software engineer should be able to present quality alternatives and their costs.