Encapsulate Modal Logic Using Subcharts

What Is a Subchart?

A subchart is a graphical object that can contain anything a top-level chart can, including other subcharts. A subchart, or a subcharted state, is a superstate of the states that it contains. You can nest subcharts to any level in your chart design.

Using subcharts, you can reduce a complex chart to a set of simpler, hierarchically organized units. This design makes the chart easier to understand and maintain, without changing the chart behavior. Subchart boundaries do not apply during simulation and code generation.

The subchart appears as a block with its name in the block center. However, you can define actions and default transitions for subcharts just as you can for superstates. You can also create transitions to and from subcharts just as you can create transitions to and from superstates. You can create transitions between states residing outside a subchart and any state within a subchart. The term supertransition refers to a transition that crosses subchart boundaries in this way. See Move Between Levels of Hierarchy Using Supertransitions for more information.

Subcharts define a containment hierarchy within a top-level chart. A subchart or top-level chart is the parent of the states it contains at the first level and an ancestor of all the subcharts contained by its children and their descendants at lower levels.

Some subcharts can become atomic units if they meet certain modeling requirements. For more information, see Restrictions for Converting to Atomic Subcharts.

Create a Subchart

You create a subchart by converting an existing state, box, or graphical function into the subchart. The object to convert can be one that you create for making a subchart or an existing object whose contents you want to turn into a subchart.

To convert a new or existing state, box, or graphical function to a subchart:

  1. Right-click the object and select Group & Subchart > Subchart.

  2. Confirm that the object now appears as a subchart.

To convert the subchart back to its original form, right-click the subchart. In the context menu, select Group & Subchart > Subchart.

Rules of Subchart Conversion

When you convert a box to a subchart, the subchart retains the attributes of a box. For example, the position of the resulting subchart determines its activation order in the chart if implicit ordering is enabled (see Group Chart Objects Using Boxes for more information).

You cannot undo the operation of converting a subchart back to its original form. When you perform this operation, the undo and redo buttons are disabled from undoing and redoing any prior operations.

Convert a State to a Subchart

Suppose that you have the following chart:

  1. To convert the On state to a subchart, right-click the state and select Group & Subchart > Subchart.

  2. Confirm that the On state now appears as a subchart.

Manipulate Subcharts as Objects

Subcharts also act as individual objects. You can move, copy, cut, paste, relabel, and resize subcharts as you would states and boxes. You can also draw transitions to and from a subchart and any other state or subchart at the same or different levels in the chart hierarchy (see Move Between Levels of Hierarchy Using Supertransitions).

Open a Subchart

Opening a subchart allows you to view and change its contents. To open a subchart, do one of the following:

  • Double-click anywhere in the box that represents the subchart.

  • Select the box representing the subchart and press the Enter key.

Edit a Subchart

After you open a subchart (see Open a Subchart), you can perform any editing operation on its contents that you can perform on a top-level chart. This means that you can create, copy, paste, cut, relabel, and resize the states, transitions, and subcharts in a subchart. You can also group states, boxes, and graphical functions inside subcharts.

You can also cut and paste objects between different levels in your chart. For example, to copy objects from a top-level chart to one of its subcharts, first open the top-level chart and copy the objects. Then open the subchart and paste the objects into the subchart.

Transitions from outside subcharts to states or junctions inside subcharts are called supertransitions. You create supertransitions differently than you do ordinary transitions. See Move Between Levels of Hierarchy Using Supertransitions for information on creating supertransitions.

Navigate Subcharts

The Stateflow® Editor toolbar contains a set of buttons for navigating the subchart hierarchy of a chart.

Tool

Description

If the Stateflow Editor is displaying a subchart, clicking this button replaces the subchart with the subchart's parent in the Stateflow Editor. If the Stateflow Editor is displaying a top-level chart, clicking this button replaces the chart with the Simulink® model window containing that chart.

Clicking this button shows the chart that you visited before the current chart, so that you can navigate up the hierarchy.

Clicking this button shows the chart that you visited after visiting the current chart, so that you can navigate down the hierarchy.

    Note:   You can also use the Escape key to navigate up to the parent object for a subcharted state, box, or function.

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