This example demonstrates modeling both structure and behavior with variability.

Feature modeling

We model features as final, that is, we do not allow dynamic reconfiguration. Feature configuration from the first snapshot remains unchanged for the entire trace.

Metamodel

Model

The optional feature express indicates the functionality of automatically closing the window. The feature pinchProtection indicates the functionality of obstacle detection and stopping the window closure.

Component and statemachine modeling

Metamodel

Simple component modeling.

Inside the components, we will embed statemachines modeling their behavior.

Model

Commands received by the window motor.

Window motor

Requests from the user. Observe, that the request expressUp is optional.

Alphabet variability

The user request expressUp is only available when the feature express is present.

Window controller with an optional component pinchDetector.

Linking the feature with the optional component (structural variability)

The component pinchDetector is only required if we support the feature pinchProtection.

Disabling objectDetected port

Without the feature pinchProtection, the port objectDetected should be inactive. Having the feature will allow receiving the signal objectDetected.

Variability in behavior using inheritance

Two kinds of window controllers:

With continuous chime

With intermittent chime

Variability in behavior using strategy pattern

We first define an abstract chiming strategy: chiming can be audible but only if active (expressed by nesting).

Concrete strategies:

Now we can parameterize the controller with a chiming strategy. Chiming should be active when moving up in express mode. The chime should be emitted only when the chiming is audible.

We can choose the chiming strategy using the following constraint:

Scenarios and properties

An example positive scenario

It must be possible to go from closed to open via partiallyOpen state

It must be impossible for the user to request opening and the window remains closed

It must be impossible for the window to be closed and continue sending motorUp command

It is a safety property to prevent burning the motor.

The window must never continue movingUp after an object was detected

It is a safety property to prevent injury.