We write a requirement shall be met if it must be fulfilled. If the feature that implements a shall requirement is not in the final system, then the system does not meet this requirement. We write a requirement should be met if it is not critical to the system working, but is still desirable.
Text in bracket such as “[ … ]” denotes informative text that is not part of the specification.
Courier font names such as
inputdenote variables or statements used in computer code.