When you create a new class, it is always a subclass of an existing class. You can create new classes with the ::CLASS directive or by sending the SUBCLASS or MIXINCLASS message to an existing class. If you specify neither the SUBCLASS nor the MIXINCLASS option on the ::CLASS directive, the superclass for the new class is the Object class, and it is not a mixin class.

Example of creating a new class using a message:

persistence = .object~mixinclass("Persistence")
myarray=.array~subclass("myarray")~~inherit(persistence)

Example of creating a new class using the directive:

::class persistence mixinclass object
::class myarray subclass array inherit persistence