Notes on Software Quality

Quality is a set of characteristics that are ultimately decided by the user, and not every user will agree on what those characteristics should be. This is why user testing of all sorts is very valuable.

You have to go back to Walter Shewhart's work and writings while at Bell Labs. In 1931's 'Economic Control of Quality of a Manufactured Product' he draws a line between 'a thing' and the human experience of it, drawing heavily from the philosophy of C.I. Lewis:

"There are two common aspects of quality: one of them has to do with the consideration of the quality of a thing as an objective reality independent of the existence of man. The other has to do with what we think, feel or sense as a result of the objective reality. In other words, there is a subjective side of quality."

He draws a line between objective quality (the measurable, physical things) and subjective quality (the human relationship to those properties).

Later in 1939's 'Statistical Method from the Viewpoint of Quality Control' he gives a good example:

"Let us take a very simple example. Suppose we consider the quality of a glass of water. We may list some of its characteristics as follows: temperature, volume, chemical purity, taste, clarity, and color. If we look at any one of these characteristics, say temperature, we see that it is impossible to specify the temperature of a glass of water to the last degree of accuracy."

I would argue this is the standard to go for when looking for a definition. Ask yourself what makes a quality glass of water and you'll immediately realize you need to ask 'according to who?'.

I didn't see this addressed in the article, and it could be more important than some of the main points.

The distinction between "measurable objective" vs. "perceptual subjective" is fundamental to understanding quality.

To add to the above; From https://en.wikipedia.org/wiki/Software_quality -

The transcendental perspective deals with the metaphysical aspect of quality. In this view of quality, it is "something toward which we strive as an ideal, but may never implement completely". It can hardly be defined, but is similar to what a federal judge once commented about obscenity: "I know it when I see it".

The user perspective is concerned with the appropriateness of the product for a given context of use. Whereas the transcendental view is ethereal, the user view is more concrete, grounded in the product characteristics that meet user's needs.

The manufacturing perspective represents quality as conformance to requirements. This aspect of quality is stressed by standards such as ISO 9001, which defines quality as "the degree to which a set of inherent characteristics fulfills requirements".

The product perspective implies that quality can be appreciated by measuring the inherent characteristics of the product.

The final perspective of quality is value-based. This perspective recognizes that the different perspectives of quality may have different importance, or value, to various stakeholders.