Developing Apama Applications > Developing Apama Applications in EPL > Defining Event Listeners > Specifying and/or/not logic in event listeners
Specifying and/or/not logic in event listeners
When the correlator creates an event listener each event template in the event expression is initially false. For an event listener to trigger on an event pattern, the event expression defining what to match against must evaluate to true. Consequently, in an event expression, you can specify logical operators.
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