1. A computing device-implemented method for generating and executing an executable representation of a first graphical model to simulate the first graphical model, the method comprising: generating the executable representation of the first graphical model, where: the first graphical model including entities, one or more of the entities is a caller entity, the caller entity is a non-graphical entity or a graphical entity, and the non-graphical entity comprises textual code; executing the executable representation of the first graphical model, wherein the executing comprises: executing a call command associated with a caller entity of the first graphical model, the call command including a name of a callee entity; identifying the callee entity based on the name of the callee entity provided in the call command; and calling the callee entity, where: the callee entity is a graphical entity in a second graphical model when the caller entity is a non-graphical entity in the first graphical model, wherein the non-graphical entity: automatically defines a new output port, the new output port being graphically represented in the first graphical model, and provides a trigger to the graphical entity at the new output port for execution of the call command, the graphical entity receiving the trigger at an input port graphically represented in the second graphical model; or the callee entity is a non-graphical entity in the second graphical model when the caller entity is a graphical entity in the first graphical model, wherein the non-graphical entity: automatically defines a new input port, the new input port being graphically represented in the second graphical model, and receives a trigger from the graphical entity at the new input port for execution of the call command, the graphical entity providing the trigger at an output port graphically represented in the first graphical model.