1. A system for knowledge representation in a computer that can enable natural language communication with a computer, comprising: a database; a builder interfaced with the database, the builder configured to construct at least one table that represents knowledge defined by one or more text expressions, each of the one or more text expressions comprising (n) operands and (n−1) operators, wherein the builder is configured to construct the table by, for each text expression, combining sub-concepts in the text expressions into higher order sub-concepts, according to precedence defined by the operators, until the higher order sub-concepts join to form a concept that represents the entire text expression, associating each of the concept and sub-concepts with a concept identifier, and storing the concept, sub-concepts, and associated concept identifiers in at least one table in the database.