The definition of a class with a single superclass begins with a
directive of the form
:- class ClassName = [SlotDef, ...] + SuperClass.
where the list of SlotDef descriptions may be empty. In that case, the definition can simplified to
:- class ClassName = SuperClass.
The class SuperClass must be a defined class when this definition is given.
In Quintus Objects, a subclass inherits all the slots of its superclass. And, by default, it inherits all the methods of its superclass. The remainder of this section describes what the programmer can do to control this inheritance.