Consider software that monitors a bank of elevators in an office building with Fn floors. The

elevator bank services all the floors. There are $Sn$ elevator shafts in the elevator bank, with

one elevator per shaft. Both Fn and $Sn$ are configurable parameters that can be updated by the

user.

$.$ The bottom floor is the underground parking garage. The first floor is the lobby. Therefore,

visitors may enter and exit the building on either the bottom floor or the lobby.

$.$ An empty elevator can either be stationary, go up$,$ or go down. A non$-$empty elevator must

move in one direction, stopping at the floors requested by the passengers before it can reverse

the direction.

$.$ The elevator doors open automatically when the elevator stops at the floor with a call button

lit. The doors close before the elevator starts moving.

$.$ There can be one or two call buttons on each floor for up and down directions. Pushed button

indicates the waiting state by the lit signal. The light turns off when the elevator matching the

called direction arrives.

$.$ An elevator car has a capacity of a maximum allowable number of riders $($elevator

passengers.$)$

The elevator properties also include a nominal speed of motion and current direction

$($stationary$,$ up$,$ or down.$)$