<class name="CompositeActor" extends="ptolemy.actor.TypedCompositeActor">
    <display name="GaussianAdderClass"/>
    <property name="ErrorStdDev" class="ptolemy.data.expr.Parameter" value="2.0">
    ...
</class>

<class name="MiniGaussianAdder" extends="CompositeActor">
    <display name="MiniGaussianAdderClass"/>
    <property name="ErrorStdDev" class="ptolemy.data.expr.Parameter" value="0.5" />
    ...
</class>