Knowledge Explorer is an interactive tool for organizing knowledge.
It helps the user to record, change and search knowledge,
and provides extensive error checking to ensure
the internal consistency of the knowledge. 
Interaction with Knowledge Explorer uses simple
English-like statements, commands and questions.

Knowledge is a representation of the facts of reality,
using words and sentences.
The internal knowledge structure consists of concept-hierarchies
and space-time-dependent events.
The principal external knowledge structures are relational databases
and transliterated English.

Principal change in version 1.5:
all commands must begin with "!".
