This Book Explores A Wide Variety Of Theoretically Central Issues In The Framework Of Head-Driven Phrase Structure Grammar (Hpsg), A Major Theory Of Syntactic Representation, Particularly In The Domain Of Natural Language Computation. Hpsg Is A Strongly Lexicon-Driven Theory, Like Several Others On The Scene, But Unlike The Others It Also Relies Heavily On An Explicit Assignment Of Linguistic Objects To Membership In A Hierarchically Organised Network Of Types, Where Constraints Associated With Any Given Type Are Inherited By All Of Its Subtypes. This Theoretical Architecture Allows Hpsg Considerable Flexibility Within The Confines Of A Highly Restrictive, Mathematically Explicit Formalism, Requiring No Derivational Machinery And Invoking Only A Single Level Of Syntactic Representation. The Separate Chapters Consider A Variety Of Problematic Phenomena In German, Japanese And English And Suggest Important Extensions Of, And Revisions To, The Picture Of Hpsg.