HPSG and Lexical Functional Grammar

This chapter compares two closely related grammatical frameworks, Head-Driven Phrase Structure Grammar (HPSG) and Lexical Functional Grammar (LFG). Among the similarities: both frameworks draw a lexicalist distinction between morphology and syntax, both associate certain words with lexical argument structures, both employ semantic theories based on underspecification, and both are fully explicit and computationally implemented. The two frameworks make available many of the same representational resources. Typical differences between the analyses proffered under the two frameworks can often be traced to concomitant differences of emphasis in the design orientations of their founding formulations: while HPSG's origins emphasized the formal representation of syntactic locality conditions, those of LFG emphasized the formal representation of functional equivalence classes across grammatical structures. Our comparison of the two theories includes a point by point syntactic comparison, after which we turn to an exposition of Glue Semantics, a theory of semantic composition closely associated with LFG.