1. A method in a computer system for performing a relationship search of a corpus of documents, each document having at least one sentence, comprising: receiving a relationship search query that designates a desired grammatical relationship between a first entity and at least one of a second entity or an action; transforming the search query into a Boolean expression; under control of the computer system, automatically determining a set of data objects that match the Boolean expression using a keyword-style search of a data structure that indexes terms of the documents in a memory of the computer system by including, for at least one of a plurality of terms, grammatical relationship information that specifies that the term is a subject, object, or modifier of another term, and including for at least one of the plurality of terms, semantic information that specifies an entity type that identifies the term as a type of person, location, or thing; and returning an indication of a plurality of matching objects in the corpus that encompass the desired grammatical relationship.