In college I am doing an assignment about the differences between (non-)functional requirements. The problem statement is as follows:
Space Invaders is a single player game. After starting the game, the
player selects a level of difficulty and starts playing the game. The
player can steer a space ship to the left and to the right and can
also shoot rockets. The goal is to destroy invaders. If a rocket hits
an invader, the invader disappears and a crash sound is played. A game
is finished when all invaders are destroyed. In this case the elapsed
time for destroying all invaders is displayed. Each player has a
personal score which can be compared with other players of the game.
While the game is running, music is being played. The game can be
paused, in which case the timer stops and the music stops playing.
During the game, the player can always see the elapsed time and a
counter of the destroyed invaders.
As far as I understand the definition, all requirements specifically listed on this statement are functional, and non functional would not be specified (availability, stability, etc.). Any thoughts?
Best Answer
Every sentence in the statement is a functional requirement. They each state a function or behavior of the game. None of them are used to judge the operation of the game, which would be a non functional requirement.
Each statement says what the game should do only in reference to itself; making them functional requirements. They each state "what".
A nonfunctional requirement states "how much". It should respond in this amount of time or it should be secured by at least 128-bit encryption. There is another element that is referenced to judge if the criteria passed or failed