BACnet has various different types of event algorithms. Each of them is implemented by a different module.

The event algorithm AccessEvent is not supported.

ASHRAE 135:

Event algorithms monitor a value and evaluate whether the condition for a transition of event state exists. The result of the evaluation, indicated to the Event-State-Detection process, may be a transition to a new event state, a transition to the same event state, or no transition. The final determination of the Event_State property value is the responsibility of the Event-State- Detection process and is subject to additional conditions. See Clause 13.2.

Each of the event algorithms defines its input parameters, the allowable normal and offnormal states, the conditions for transitions between those states, and the notification parameters conveyed in event notifications for the algorithm. When executing an event algorithm, all conditions defined for the algorithm shall be evaluated in the order as presented for the algorithm. Some algorithms specify optional conditions, marked as "Optional:" Whether or not an implementation uses these conditions is a local matter. If no condition evaluates to true, then no transition shall be indicated to the Event-State-Detection process.