Suppose a requirement is "The automated interfaces of the system must be easy
to learn". There is no obvious measurement scale for "easy to learn". However if
we investigate the meaning of the requirement within the particular context, we
can set communicable limits for measuring the requirement.
Again we can make use of the question: "What is considered a failure to meet
this requirement?" Perhaps the stakeholders agree that there will often be
novice users, and the stakeholders want novices to be productive within half an
hour. We can define the quality measure to say "a novice user must be able to
learn to successfully complete a customer order transaction within 30 minutes of
first using the system". This becomes a quality measure provided a group of
experts within this context is able to test whether the solution does or does
not meet the requirement.
An attempt to define the quality measure for a requirement helps to
rationalise fuzzy requirements. Something like "the system must provide good
value" is an example of a requirement that everyone would agree with, but each
person has his own meaning. By investigating the scale that must be used to
measure "good value" we identify the diverse meanings.
Sometimes by causing the stakeholders to think about the requirement we can
define an agreed quality measure. In other cases we discover that there is no
agreement on a quality measure. Then we substitute this vague requirement with
several requirements, each with its own quality measure.
Does each requirement have a quality
measure that can be used to test whether any solution meets the requirement?
