Simulating a statechart model means to execute it, raise events manually, have time-based and other events being triggered automatically, and observe the model’s behavior.
You can run multiple state machines in parallel and even multiple instances of the same state machine.
An introduction to simulation is given in section "Simulating the light switch model".
You have several options to start a statechart simulation.
The most direct way is to start the simulation based on the statechart model file.
Selecting Run As → Statechart Simulation in the context menu
In order to re-run the simulation you have most recently executed, simply
[Ctrl+F11]on the keyboard
To be exact, this operation does not necessarily re-run the last
simulation, but rather the last executed
launch. So if, for example, you first run a statechart simulation followed by running a Java program, then upon pressing
[Ctrl+F11] that Java program is executed once again, not the statechart simulation.
Let’s consider a scenario where you want to execute a simulation that you have run before, but not as the most recently executed launch. So you cannot use the procedure described in section "Repeating the last simulation".
However, as long as you haven’t launched too many other programs in between, chances are good to find your simulation in the history.
Try the following:
When a statechart is simulated for the first time, a launch configuration is automatically created. A launch configuration describes the parameters used for a particular launch. In case of a statechart simulation, it describes which statechart is to be simulated and the simulation mode (event-driven or cycle-based). For details on how to create and modify a launch configuration, see section "Configuring a simulation".
To execute an existing launch configuration, proceed as follows:
The SC Simulation perspective provides selected views that are most useful when running a statechart simulation.
When a simulation starts, the perspective usually changes to the SC Simulation perspective. If this doesn’t happen, you can manually engage the SC Simulation perspective as follows:
Alternatively, you can do the following:
By default, the SC Simulation perspective shows the following views:
The SC Simulation perspective also includes the statechart editor. In a running simulation, the statechart editor highlights active states by coloring their backgrounds in red.
When a transition is taken, the transition arc leading from the source state to the target state flashes briefly in red. After that, the target state becomes active and changes its background color to red. The source state’s background color becomes normal again.
The SC Simulation perspective
The Simulation view is used to manually raise events and to inspect and modify variables of a running simulation. By default that view is located on the right-hand side of the SC Simulation perspective, see figure "Simulation view" for an example.
The Simulation view groups events and variables by their interfaces. The unnamed interface appears as default in the interface list. Click on the small triangle left from a interface’s name to show or hide the interface’s contents, i.e., events and variables.
Depending on your screen resolution and font size settings, you might not be able to spot the Simulation view by its name, because the tab containing it is quite narrow and might not provide enough space for displaying the title. Hover over the tabs to reveal their respective titles in a popup window.
Figure "The SC Simulation perspective" is demonstrating this: The user has hovered the mouse pointer over a tab that is just displaying the starting letter ‚S’ of its title. However, a popup window right besides the pointer is showing the tab’s full title „Simulation”.
Simulation view – The actual Simulation view is the pane right from the statechart editor.
You can interact with a running simulation by manually raising events and by inspecting and modifying variables. You can do so at any point in time, but in most cases you will do so while the simulation „sits idle” at its active state and waits for an event to trigger a transition.
To raise an event, proceed as follows:
To inspect a variable’s value, proceed as follows:
Watch the displayed values change as the simulation progresses and actions in states or transitions are executed that modify the variables' contents.
To manually modify a variable’s value, proceed as follows:
[Enter]. The new value is assigned to the variable and replaces the former value.
Section "Creating and executing a launch configuration" describes how to start an existing launch configuration.
The present section describes how to create and configure a new launch configuration for a statechart simulation.
New_configurationto something sensible, e.g.,
Besides the Main tab described above, a statechart simulation launch configuration also has a tab named Common. This tab is a common standard to all types of launch configurations, and thus it is not documented here.
In addition to creating new launch configurations, you can also duplicate or delete launch configurations in the Run Configurations dialog. Right-click on a launch configuration and select Duplicate or Delete from the context menu.
This advanced feature makes it possible to attach breakpoints to states and transitions. If a statechart simulation reaches a transition or a state with a breakpoint, it suspends execution of the simulation. A breakpoint can be amended with a condition in order to suspend the simulation only if the condition is fulfilled (true).
You can also create snapshots of your statechart simulation. A snapshot contains everything making up your state machine simulation at any point in time. It describes the state of the state machine, if you will. Snapshots can be saved and restored later in order to continue the simulation from that point on that is specified by the snapshot.
Throughout this chapter we will be using the light switch statechart as an example. It models a lamp which can be turned on and off and also supports various brightness values.
If you press the pressLightOn button, the lamp turns on at its lowest brightness value. If you operate pressLightOn repeatedly, each time the lamp becomes brighter until it reaches its maximum brightness. Pressing the pressLightOff button, immediately turns off the light completely. The brightness can only be raised as long as it hasn’t yet reached its maximum value of five. After that, the guard condition disallows to raise it any further.
The light switch sample statechart
Breakpoints allow for automatically suspending the simulation when a certain element of the state machine is activated. Optionally, a halting condition can be specified to better control the behavior of a breakpoint. Breakpoints can be set on transitions or states. When a breakpoint is reached, the simulation pauses and the current state of variable values can be examined in the simulation view. It is possible to change values and to trigger events that will be raised when the simulation run is manually resumed.
To make use of breakpoints, the statechart simulation needs to be executed in debugging mode:
Starting a simulation in debugging mode
Setting a breakpoint
States and transitions having a breakpoint attached are labeled with a symbol. Figure "Breakpoints on transition and state" shows an example.
Breakpoints on transition and state
If the simulation runs into a state with a breakpoint, the state’s entry actions, if any, are executed. After that, execution of the state machine is suspended. The state is highlighted by a small green border.
Highlighting a suspended state
If the simulation runs into a transition with a breakpoint, execution of the state machine is suspended. The transition is highlighted by drawing the transition arrow in green. The transition’s actions, if any, are executed when the state machine is resumed.
Highlighting a suspended transition
In order to continue from a breakpoint, you have two options:
The breakpoints view shows a list of all breakpoints. The respective breakpoint name identifies the state or transition in question. See figure "Breakpoints view" for an example.
You can use the breakpoints view for disabling, enabling, and removing breakpoints as well as defining conditional breakpoints.
The Breakpoints view
A breakpoint is either enabled or disabled.
Figure "Breakpoints view" is showing an enabled and a disabled breakpoint in the statechart editor and in the breakpoints view, respectively.
You can instruct the statechart simulation to skip all breakpoints by clicking at the button in the breakpoints view. The button will appear „pressed”, and while it is, the „skip breakpoints” functionality is engaged. That means, the simulation will not suspend at any breakpoint.
This is different from disabling all breakpoints, in that each breakpoint keeps its state of being enabled or disabled. Once you disengage the skip breakpoints functionality by clicking at the button again, the simulation will suspend again at enabled breakpoints and will not suspend at disabled breakpoints.
In order to remove some breakpoints, select these breakpoints in the breakpoints view, then click at the button. The selected breakpoints will be removed.
To remove all breakpoints, click at the button
A conditional breakpoint has an associated condition and suspends the simulation only if
In order to attach a condition to a breakpoint, proceed as follows:
Enter the condition into the text field. Like in the statechart editor, a content assist is available when pressing
[Ctrl+Space]. The expression is validated automatically. In the example shown in
figure "Breakpoints view" the transition suspends the simulation only if the variable
brightness has a value of 4.
In the suspended status of a statechart simulation you can change variable values using the simulation view. When continuing execution – see section Continuing the simulation – you can observe how your state machine behaves with those modified values.
If you click on an event’s name in the simulation view to raise that event in normal simulation, i.e., while execution isn’t suspended, the state machine immediately processes that event and takes the corresponding transition, if any.
However, while the simulation is suspended, you can raise multiple events, without instant execution. Once execution resumes, both events are handled at the same time, or, to be more exact, in the same run-to-completion step (RTS).
Consider for example, you want to press the "light on" and "light off" buttons at the same time and observe what happens. Figure "Raising multiple events simultaneously" is showing the scenario:
Raising multiple events simultaneously 
Raising multiple events simultaneously 
Both events are raised and will be handled by the state machine during the next run-to-completion step. The latter will be performed as soon as the user clicks on the step-over button or the resume button .
Please note: While the execution is still suspended, you can „unraise” an already raised event by clicking at the event symbol a second time. The blue triangle will disappear, and upon continuation of the simulation the event will not be handled.
It is important to understand that there is not queue of events. That is, in case several events occur simultaneously, the state machine consults the active state’s transitions priorities in the order that is specified in the corresponding property, see figure "Transition priorities". You can change the transitions priorities by selecting a transition and moving it up or down by clicking at the respective button.
The first transition whose condition is fulfilled will be executed. All remaining events are quashed.
The snapshot feature allows to store and restore the state of a simulation run. A snapshot comprises all active states of the state machine as well as all variable values at the time of snapshot creation.
This feature is especially useful when testing complex state machines in which a number of steps need to be taken before reaching a desired situation. Using snapshots, you can store this desired situation once and simply restore it again without repeating all the steps to reach it. Depending on the complexity of the usecase, this can be a huge time-saver.
To create a snapshot of the current statechart simulation, proceed as follows:
A freshly taken snapshot
The snapshots view consists of two parts.
Inspecting snapshot details: variables overview [left], image overview [right]
To restore a snapshot for execution, proceed as follows:
Please note: When the semantics of the underlying state machine have been changed, it might not be possible to restore a snapshot, e.g., when the active state has been deleted.
The label of a snapshot can be changed as follows:
[Return]or click anywhere outside the editable field.