PTOLEMY II - CiteSeerX

Using Vergil
resulting icon for the subclass appears right on top of the icon for the class, so it needs to be moved
over, as shown in the figure.
Looking inside the subclass reveals that it contains all the elements of the class, but with their
icons now surrounded by a dashed pink outline. These elements are inherited. They cannot be removed
from the subclass (try to do so, and you will get an error message). You can, however, change their
parameter values and add additional elements. Consider the design shown in figure 2.40, which adds
an additional pair of parameters named “interferenceAmplitude” and “interferenceFrequency” and an
additional pair of actors implementing the interference. A model that replaces the last channel with an
instance of the subclass is shown in figure 2.41, along with a plot where you can see the sinusoidal
interference.
An instance of a class may be created anywhere in a hierarchical model that is either in the same
composite as the class or in a composite contained by that composite. To put an instance into a sub-
FIGURE 2.37. The model from figure 2.36 with the icon changed for the class. Note that changes to the
base class propagate to the instances.
FIGURE 2.38. The model from figure 2.37 with the icons of the instance changed to override parameter
values in the class.
70 Ptolemy II