Reading the wikipedia doc, It seems that a
knowledgebase does not only contain data in a "Rule Format" but
even other kind of information. For instance
information like the "object model".
As far as I understood the rulebase does not
contain anything related to the object\fact model.
So I would say that the rulebase is "part of" the
knowledge base and not the "knowledgebase" itself.
It's just an idea....
Massi