A framework is presented for the supervisory control of nondeterministic discrete-event systems based on failure semantics, It guarantees deadlock-free behavior under all circumstances, it allows for powerful specifications, it forms a sound basis for modular control, and it can handle nondeterminism without extra effort, A synthesis method to generate the least restrictive supervisor is presented. Secondly, the control problem with partial specification is formulated, and it is shown that this control problem can be rewritten to a control problem with full specification, Special care has to be taken for traces with an unbounded internal extension (divergence), A condition, denoted bounded recurrence, is introduced to handle these traces, It is shown that the external behavior of the controlled system is not restricted by this condition.