1. A method in a computer system for transforming a document into a canonical representation using entity tags, each entity tag having a type and an associated value, the document having at least one sentence, comprising: receiving a designation of a plurality of entity tags; and for each sentence, parsing the sentence to generate a parse structure having a plurality of syntactic elements; determining from the parse structure a set of syntactic elements that correspond to the designated entity tags; and storing in an enhanced data representation data structure a representation of each association between a syntactic element of the determined set of syntactic elements and the type of the entity tag that corresponds to the syntactic element, the syntactic element representing the value of the corresponding entity tag, such that the sentence is represented in the data structure by at least one entity tag.