Unnamed classes may be defined by the macro def-kb-class which takes the same arguments as the
macro. It is identical to using defclass and supplying the KnowledgeWorks mixin standard-kb-object if none of the superclasses already contains it. The function
may be used to create instances of the class.
KnowledgeWorks and Prolog User Guide (Macintosh version) - 6 Dec 2011