An event expression is a special type of expression that is used with the on statement (see The on statement) to define the rules for detecting events of interest and invoking an action when a matching event is detected. In an event expression, you can specify filtering rules based on an event’s field values, sequencing rules for events followed by other events, times and time ranges during which an event is of interest, and other rules.

Event expressions should not be confused with ordinary EPL expressions of type event. Ordinary EPL expressions of all types are described in Expressions.

The on statement is discussed in The on statement, but because the on statement and event expressions are so closely related, here are the on statement diagrams: