Software Quality Model
In the context of software engineering, software quality refers to two related but distinct notions that exist wherever quality is defined in a business context:
- Software functional quality reflects how well it complies with or conforms to a given design, based on functional requirements or specifications. That attribute can also be described as the fitness for purpose of a piece of software or how it compares to competitors in the marketplace as a worthwhile product;
- Software structural quality refers to how it meets non-functional requirements that support the delivery of the functional requirements, such as robustness or maintainability, the degree to which the software was produced correctly.
Structural quality is evaluated through the analysis of the software inner structure, its source code, at the unit level, the technology level and the system level, which is in effect how its architecture adheres to sound principles of software architecture outlined in a paper on the topic by OMG. In contrast, functional quality is typically enforced and measured through software testing.
Historically, the structure, classification and terminology of attributes and metrics applicable to software quality management have been derived or extracted from the ISO 9126-3 and the subsequent ISO 25000:2005 quality model, also known as SQuaRE. Based on these models, the Consortium for IT Software Quality (CISQ) has defined five major desirable structural characteristics needed for a piece of software to provide business value: Reliability, Efficiency, Security, Maintainability and (adequate) Size.
Software quality measurement quantifies to what extent a software or system rates along each of these five dimensions. An aggregated measure of software quality can be computed through a qualitative or a quantitative scoring scheme or a mix of both and then a weighting system reflecting the priorities. This view of software quality being positioned on a linear continuum is supplemented by the analysis of "critical programming errors" that under specific circumstances can lead to catastrophic outages or performance degradations that make a given system unsuitable for use regardless of rating based on aggregated measurements. Such programming errors found at the system level represent up to 90% of production issues, whilst at the unit-level, even if far more numerous, programming errors account for less than 10% of production issues. As a consequence, code quality without the context of the whole system, as W. Edwards Deming described it, has limited value.
Read more about Software Quality Model: Motivation, Definitions, Alternative Approaches, Measurement, See Also, References
Famous quotes containing the words quality and/or model:
“Although good early childhood programs can benefit all children, they are not a quick fix for all of society’s ills—from crime in the streets to adolescent pregnancy, from school failure to unemployment. We must emphasize that good quality early childhood programs can help change the social and educational outcomes for many children, but they are not a panacea; they cannot ameliorate the effects of all harmful social and psychological environments.”
—Barbara Bowman (20th century)
“The playing adult steps sideward into another reality; the playing child advances forward to new stages of mastery....Child’s play is the infantile form of the human ability to deal with experience by creating model situations and to master reality by experiment and planning.”
—Erik H. Erikson (20th century)