1. A database reverse-query system coupled to a computer readable storage medium, said database reverse-query system comprising: a match component that analyzes text from a document and identifies preliminary query phrases that match at least a portion of text in the document; and a generation component that generates a canonical table, a Boolean table, and an expression table, the canonical table including canonical expressions formed at least in part as sub-expressions derived from the preliminary query phrases, the Boolean table specifying logic relationships among the canonical expressions, and the expression table comprises a mapping of preliminary query phrase identifiers to canonical expression identifiers based on the Boolean table, wherein the Boolean table is populated the with child expression identifiers each corresponding to a respective child expression, Boolean weights for each child expression, parent expression identifiers, and parent expression target weights, and wherein said Boolean table produces the same parent expression identifier whenever the child expression identifiers and the Boolean weights are the same.