Reliable signaling between outputs and inputs is provided. Inputs and outputs are allowed to be mutable and thus can change. The change of an output affects inputs connected to it. Thus, when write access is requested for an output, a notification is sent to inputs connected to it. The change may be made and then write access may be released signaling that the change is completed. A notification that the change has been completed is then sent from the output to the inputs. This allows a user to know when exactly the change occurred and ended.