more about query Expansion

knowledge base--- knowlege based in this context is about terms would be used by search engine user, and map to terms used by search engine vendor, as well as ontology information.
KB = {[concept terms {[class belief] ]}*
here
concept--terms would be used by search engine users.
terms ---terms used by search engine vendor.
class --- ontology class.

Example,

class University {
Name:
Subjects:
Location:
}

One of possible knowlege Item about this is:
[concept="MIT" terms="Massachusetts Institute of Technology" class=University belief=0.98];