After some thought, I decided I needed to provide a little more context about functional requirements before we move on to the mockup phase. Requirements require satisfaction in order to achieve sign-off in the design and development stages of the process so I wanted to cover them briefly here.
During the design phase, a functional requirement is satisfied when it is represented by either a user interface mockup or technical specification. Being satisfied in the design phase indicates that the requirement has been considered, addressed, and will be represented in the final implementation.
After the design phase, in support of the development phase, acceptance criteria should be applied to each requirement. Each requirement will typically have one or more test cases attached to it that if all pass, prove that the requirement has been satisfied. At different stages throughout the development process, the test cases are executed against the software to establish which requirements have been satisfied and which have regressed and are no longer satisfied.
We will cover this in more detail later in the series.