Some subsystems can be specified as optional, if omission of such a subsystem will not lead to ambiguity. This means that the subsystem can be omitted in the command line. The optional subsystems are bracketed ("[]"). For example, if the full command specification is written as:
SOURce:POWer[:LEVel]:SLOPe[:DATA]
subsystems LEVel and DATA are optional. Therefore, both commands are valid:
SOURce:POWer:LEVel:SLOPe:DATA
SOURce:POWer:SLOPe