Make The Requirement Measurable

"The idea is for each requirement to have a quality measure that makes it possible to divide all solutions to the requirement into two classes: those for which we agree that they fit the requirement and those for which we agree that they do not fit the requirement."

In other words, if we specify a quality measure for a requirement, we mean that any solution that meets this measure will be acceptable. Of course it is also true to say that any solution that does not meet the measure will not be acceptable.
The quality measures will be used to test the new system against the requirements. The remainder of this paper describes how to arrive at a quality measure that is acceptable to all the stakeholders.

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.

Another test for completeness is to question whether we have captured all the requirements that are currently known. The obstacle is that our source of requirements is people. And every person views the world differently according to his own job and his own idea of what is important, or what is wrong with the current system. It helps to consider the types of requirements that we are searching for: