What is important, that ony one instance of the same name may be used in a module, and a class cannot be redefined if instances of the class exist. Go get slot of current instance just type? An object's behavior is defined by its message-handlers handlers. In object-oriented programming a class is a template which describes the common characteristics or attributes of objects. The alternative way is to use dynamic-get and dynamic-put :. CLIPS automatically provides handlers:. Handler-type tell when to execute the handler.