This model is intended to help understand and explain the relationship between four words which are critical to the vocabulary of a tester:
- Value – the worth or usefulness of something
- Quality – the subjective and variable perception of that value
- Risks – anything which threatens that value
- Testing – how we discover information relating to value and to risks
You may recognize that the definition of Quality is largely based on the Gerald Weinberg definition:
“Quality is value to some person”
and on the enhancements made to this definition by Michael Bolton and James Bach, and in a blog post from Markus Gärtner (references at the foot of this post).
I’ve also included the word ‘perceived‘ because, as I discussed in last week’s post, ‘Perception Matters‘, value must be perceived to be delivered, and there are many factors which might affect that perception.
Risks represent anything which might threaten value to that person who matters. These might be product risks relating to quality criteria or they may be project or business risks. (The focus on threats to value rather than ‘defects’ or ‘bugs’ is also based on the work of Michael Bolton and James Bach and again there are some references below.)
As we explore these risks through our testing we might identify problems, or with a deeper understanding we might uncover new areas of risk which warrant further investigation.
We will also discover information relating to the value of the product, and perhaps the experience of using it for those people who matter.
- Quality is value to some person – Gerald Weinberg (from Quality Software Management: Volume 1. Systems Thinking p. 7.)
- Quality is value to some person (who matters) – Michael Bolton and James Bach
- Quality is value to some person at some time – Markus Gärtner’s blog