Functional and Nonfunctional Requirements – Georgia Tech – Software Development Process
Among the requirement that we can collect from the application domain, we need to distinguish between two main types. And you’ve, probably heard about these ones. Functional requirments and non-functional requiremnts.
. Functional requiremetns have to do with the functionality of the system with what the system does with the computation.. For example, the elevator shall take people to the floor. They select. That’s, a functional requirement that has to do with the functionality of the system.
Or for a very simple one. The system has to output the square root of the number past as an input., So these kind of requirements have in general. Well defined satisfaction criteria., So, for example, if for the latter, one that we mentioned, it is pretty clear how to check whether the output is actually the square root of the number passed in input.
Non-functional requirements. Conversely, refer to a system’s, non-functional properties systems, qualities. Such as security accuracy, performance cost. Or you know, usability adaptability, interoperability, reusability and so on.
. So all these qualities, the don’t necessarily have to do with the functionality. And unlike functional requirements. Non functional requirements Do not always have clear satisfaction criteria., For example, if we say that the elevator must be fast, that’s, a non-functional requrement.
Right. It has to do with the speed of the elevator, which is a quality of the elevator., But it it’s, not clear how such a requirement could be satisfied.. How could we tell whether the elevator is fast or not.
? So what we need to do in these cases Is that we need to refine these requirements so that they become verifiable. For the example that I just mentioned. For instance, we might say that the elevator must reach the requested floor in less than 30 seconds.
From the moment when the floor button is pushed., This is still a non-functional requirment, but is a verifiable one.