Through Java APIs, a simulation execution starts when the specific element is executed. You can start the execution, stop the execution, and create and register a new Simulation Execution Listener using Java APIs. Regarding the core component of the entire execution mechanism, the execution engine defines how to execute a set of Element types. fUML Helper is also available as a Class that provides Helper methods related to the fUML structures. The Parametric engine also provides Java APIs for a parametric execution with a runtime object of a Classifier.