8.1.3 Members of Model Classes

The following constants are defined in each model class. They contain information about the model structure.

• private static final int StateNum. The number of states in the model, not including the states in its submodels.

• private static final String[] EventNames. The names of the events to be handled by the model, not including the events handled by its submodels. The indexes of those event names represent their IDs. Those IDs start from 0.

• private static final String[] StateNames. The full paths of the states in the model, not including the states in its submodels. The indexes of those full paths represent the IDs of the states. Those IDs start from 0.

• private static final int[] ParentTable. The table of parent-children relations in the model. ParentTable[i] contains the ID of the parent of state i. This is the inverse of the $C$ function in the abstract syntax.

• private static final boolean[][] Hierarchy. The children function of the model (the same as the $C$ function in the abstract syntax). Hierarchy[i] is an array over all the states. Hierarchy[i][j] is true if and only if state j is a child of state i.

• private static final int[] HistoryStateTable. The definition of history states in the model. Each element in this array has the following meaning:
  
  $$HistoryStateTable[i]=\left\{ \begin{array}{ll} 0, & if\ s... ... if\ state\ i\ has\ a\ deep\ history \\ \end{array} \right.$$
  
  

• private static final String[] LeafStateTable. The definition of leaf states in the model, including importation states if any. If state i is a leaf state, LeafStateTable[i] is equal to the full path of state i; otherwise, LeafStateTable[i] is equal to null.

The following are the Java data structures to store the state of the model at run-time:

• private State state. The current leaf state list of the model. Class State is a linked list of state IDs.

• private StateMachine[] Submodels. The submodels of the model. Submodels[i] is not null if and only if state i is an importation state and the submodel in it has been loaded. Once the submodel is loaded, it is never deleted even if the model leaves the importation state. The history recorded in the submodel object is the history of the importation state.

• private History[] history. The history of each state in the model. history[i] is not null if and only if a history is recorded for state i. Class History is an internal structure that records a single history. Its value is changed as the model enters the state again and leaves it from another substate.

As all of the attributes of a model class are private members, the users can only access them by means of public methods. The following list includes some of the important methods:

• public modelname(). Constructor of the model class. (modelname is the name of the model.) The required data structures are initialized. However, the model is not initialized. Its current state is illegal.

• public void initModel(). Initializes the model. This means to place the model in its default state(s). The initializer of the model is executed.

• public boolean isInState(String s) and public boolean isInState(int s). These two functions check whether the model is in a certain state. The state can be specified with its full path or with its integer ID. The second method is more efficient since it does not require string comparison. The method with a string parameter is kept only for interaction with the model users, who do not know the internal state IDs.

• public boolean handleEvent(String se). The handler of any event. The event is given as a string, and this function automatically converts the string into its integer ID for internal use. It tests the event ID with a switch-case control structure. It checks the source states of the transitions and their guards. If any enabled transition is found, the state variables are changed according to the original design of the DCharts model. This method also executes the output and the enter/exit actions (if any) as the transition is fired. If the model changes to a final state, it also executes the finalizer before returning.

• public void changeState(int s1, int s2, boolean check_history). Changes the model from state s1 to s2. This method implements the state change triggered by a transition from state s1 to s2. If check_history is true, the history of s2 or any state in the path from state $Common(s1,s2)$ to state s2 is considered (such a transition has a [HS] property in the original DCharts model); otherwise, history is ignored even if it is recorded.

  public void changeState(int s1, int s2) is equivalent to public void changeState(int s1, int s2, false).

• protected int eventStr2Int(String event). Converts a string event name into its integer ID.

• protected StringList getCurrentStateList(). Retrieves the current leaf state(s) of the model. The result is stored in a linked list of strings. Its elements are instances of class StringList. This method looks up all the current leaf states in the main model, as well as the current leaf states in all the submodels. It is used internally in the Java class. To retrieve the current states in a more understandable format, the designers should use function public String getCurrentState().

• public String getCurrentState(). This method invokes method protected StringList getCurrentStateList(), and returns the current leaf state(s) as a string enclosed by a pair of square brackets. Multiple states are separated by comma `` ,''.

• public int getParentState(int state). Returns the parent state of the specified state.

• public boolean isHistoryState(int state). Tests if the specified state has a history.

• public boolean isLeafState(String state). Tests if the specified state is a leaf state.

• public Hierarchy getHierarchy(int start_level, String state_prefix). Returns the state hierarchy structure of the model. The hierarchy structure is a linked list. The Next attribute of each element (if it is non-null) gives access to the next element. Each element in this linked list has the following attributes:
  • public String StateName. The name of a state in the model.

  • public String PathName. The full path of the state.

  • public int StateNum. The integer ID of the state.

  • public int Level. An integer that denotes the level which the state is at. The larger this number is, the deeper the state is in the state hierarchy.

  Parameter start_level is an integer to be added to the Level attributes of all the elements in the returned list. This is useful for importation states. Suppose an importation state is at level 5. It calls the getHierarchy method of the imported model with start_level=5. The generated hierarchy starts from level 6.

  Parameter state_prefix is the prefix to be added to the head of the PathName attributes of all the elements in the returned list. For example, importation state ``A.B'' calls the getHierarchy method of the imported model with state_prefix="A.B". The full paths in the generated hierarchy start with ``A.B.''.