In EPL programs (monitors), you can use standard EPL plug-ins provided with Apama and you can also use EPL plug-ins that you define yourself. An EPL plug-in consists of an appropriately formatted library of C++ functions, which can be called from within EPL code. In the case of a plug-in written in Java, the Java classes that are called from an application's EPL code are contained in a jar file. The correlator does not need to be modified to enable or to integrate with a plug-in, as the plug-in loading process is transparent and occurs dynamically when required.

To write custom EPL plug-ins, see Developing EPL Plug-ins.

When using a plug-in, you can call the functions it contains directly from EPL, passing EPL variables and literals as parameters, and getting return values that can be manipulated.