Writing Monitors for the Event Monitoring Service (December 1999)

Chapter 2 49
The EMS Application Programming Interface (API)
Function Descriptions
recovery is not required of resource monitors, however.
Some resource monitors have the ability to asynchronously detect
changes in the resource values they support. For example, a resource
monitor that uses the rm_select_data structure in
rm_get_next_event() might be notified via a named pipe that a
resource value has changed. In these circumstances, it is acceptable for a
resource monitor to create a Resource Update object and call
rm_notify() immediately. The basic idea is that target applications
want to know as soon as possible if the resource value meets the
notification criteria. Monitors that are sufficiently sophisticated to
provide this function are encouraged to do so. Asynchronous notification
is not required, however.