An example of a capability requirement is the stimulus-response behavior of a single button. An example of a quality requirement is usability,
or the time to perform a task, in which pressing the button may be only a single step. Capability and quality requirements are similar in that both are black box (or externally detectable) information. However, in most other respects such as utility, traceability, and measurement, they are very different as evidenced by Table 5.1.