Overview

Head-driven phrase structure grammar (HPSG) has evolved as a synthesis of ideas from a number of theoretical sources, including generalized phrase structure grammar (GPSG), categorial grammar, and formal theories of data structure representation (e.g., the PATR-II formalism and Kasper-Rounds logics of computation). In the course of more than a decade of development these theoretical resources have been applied to a monostratal theory of linguistic structure which is capable of providing a formally explicit grammar for any given natural language. HPSG uses a fundamental theoretical strategy made familiar by GPSG: the enumeration of a class of objects, corresponding to expressions of some natural language, and a set of constraints whose interaction enforces the appropriate covariation of formal properties reflecting the dependencies that any grammar of that language must capture.

A head-driven phrase structure grammar of some language defines the set of signs (form/meaning correspondences) which that language comprises. The formal entities that model signs in HPSG are complex objects called feature structures, whose form is limited by a set of constraints – some universal and some language-parochial. The interaction of these constraints defines the grammatical structure of each such sign and the morphosyntactic dependencies which hold between its subcomponents. Given a specific set of such constraints, and a lexicon providing at least one feature structure description for each word in the language, an infinite number of signs is recursively characterized.