EPL has primitive types and reference types. Data in the primitive types are simple scalar values. Reference types (also called complex types or object types) have values that are more complicated and some, like the dictionary type, have multiple values and have definitions that involve more than one type.

When values are passed as parameters in action and method invocations, primitive types are passed by value, and reference types are passed by reference. When a parameter is passed by value, the called action or method receives a copy of the value and has no direct way to change the variable that the value may have been derived from. When a parameter is passed by reference, the called action or method receives a reference instead of a copy and if the called action changes the value, the caller also sees the change.

Note that there is no type equivalent to a memory address or pointer.