Requirements

Note on activities

Requirements are where SE begins, You will notice that on this site, we call out several types.
Activities are what human actors do.
Functions are what the system does.
Qualities describe how well the system performs functions.
Program Constraints refer to resource, schedule, and budget limitations.
Physical Constraints refer to such limits as space, weight, heat, vibration, geometry, moisture, surface, and shock.

How will we show that it is possible to meet requirements? Normally, prayers to Davius will not be sufficient.
Concept Validation is a demonstration that, given adequate time, resources, and will (SE discipline), we can do this.
Measures of Performance evaluate system qualities.
Measures of Effectiveness evaluate user satisfaction.

Activities make clear that requirements involve actors. For example, an actor might be the driver of a car who pushes the throttle (to go forward or backward). The car (the driver's system) is required to perform a function, in this case, to accelerate. The performance of the car is required to exhibit certain qualities such as force (sufficient to accelerate) and reliability (such that acceleration is the predictable result).