8.2.5 Importation

Importation is transformed into instantiation in the synthesized code. A class is generated for each model. When a submodel is imported, the importing model instantiates an object of the submodel class, and associates the new object with the ID of the importation state.

According to the DCharts semantics, an imported model is conceptually a part of the importing model. Once imported, it remains until the simulation or execution finishes. All the states and transitions of the imported model are copied to the inside of the importation state. This semantics is implemented as instantiation as follows:

• Once an object of a submodel class is instantiated and associated with a state ID, it is not deleted until the execution of the top-level model finishes (or, usually until the program exits).

• When the model leaves an importation state, the object associated with it is kept as its history.

• If history is recorded for an importation state, it is restored when the model goes to that state because of the firing of a transition with the [HS] property. If the state has a history but the transition does not have the [HS] property, the submodel is re-initialized to its default states. In the latter case, for simplicity, the importing model instantiates a new object of the submodel class, and replaces the old one with it. The old submodel object is recycled by the Java garbage collector.

• For each model, the configuration of submodels, including their number and the states that import them, is fixed and can be decided statically. The array Submodels of a model class keeps track of all those submodels.