Application level triggered, and edge triggered event multiqueues.
A system for providing late binding for how different types of events are handled.
It is often important for an application to control how it consumes updates for optimal processing, but event sources are typically in control of delivery. The EQueue abstraction allows the consumer to provide an implimentation that balances delivery for its needs. To do this, it distinguishes events into two types, level and edge triggered.
Level triggered events are used where the resulting state is cared about and a pure model of how events combine is available as a Semigroup instance. The transitions it took to get to the new state between dequeues is not of interest.
Edge triggered events are where the sequence of occurences are of importance, or a pure model is not available.