EPL is a flexible and powerful curly-brace, domain-specific, language designed for writing programs that process events.

In EPL, an event is a data object that contains a notification of something that has happened, such as a customer order was shipped, a shipment was delivered, a sensor state change occurred, a stock trade took place, or myriad other things. Each kind of event has an event type name and one or more data elements (called event fields) associated with it. External events are received by one or more adapters, which receive events from an event source and translate them from a source-specific format into Apama's internal canonical format. Derived events can be created as needed by EPL programs.