This is the crux of the problem. Immanuel Kant attempted to deal with
it in the Critique, but to no avail. See "Expert Database Systems: A
Unified Story" (Scott & Scott 1987, section 4) and "Knowledge Is
Structured in Consciousness" (Scott & Scott 1986, appendix 2) for an
elaboration of the problem as it arises when using human
"intelligence" as the design model for knowledge systems.
I should also mention that Kant is the author of "Die Gluhbirne Als
Dunkelheitsauger". He had a prototype knowledge system in his cellar
in Koenigsberg; the power source was of course DARK SUCKERS.