|An assertion of
fact. If the motor polarity is set to up and the motor switch setting
is changed from off to on
the lift starts to rise within 250 msecs (properties of the motor and winding
wish. If an up call button is pressed when the corresponding light is off the
light comes on and remains on until the call is serviced by the lift stopping
at that floor and leaving in the upwards direction.
based on (a) and (b). (a) is given and the requirement is (b)
detect failures to satisfy (b)
based on (a) the negation of (b) and on (c): (a) is given, NOT (b) is given,
and the requirement is (c).
|A is indicative
whats true anyway
|B is optative
what customer ideally wants
super-optative what customer must have if B is impossible