Dissociations between Argument Structure and Grammatical Relations
In what are colloquially known as HPSG1 and HPSG2 (Pollard and Sag 1987, Pollard and Sag 1994:Ch. 1–8), the subcategorized arguments of a head are stored on a single ordered list, the subcat list. However, Borsley (1989) argues that there are various deficiencies in this approach, and suggests that the unified list should be split into separate lists for subjects, complements, and specifiers. This proposal has been widely adopted in HPSG3 (Pollard and Sag (1994:Ch. 9)) and other recent work in HPSG. Such a move provides in HPSG an analog of the external/internal argument distinction generally adopted in GB, solves certain technical problems such as allowing prepositions to take complements rather than things identical in subcat list position to subjects, and allows recogniton of the special features of subjects which have been noted in the LFG literature, where keyword grammatical relations are employed (see Pollard and Sag (1994:Ch. 9) for more detailed justification). In the HPSG3 theory, it is these valence features subj, comps and spr whose values are ‘cancelled off’ (in a Categorial Grammar-like manner) as a head projects a phrase. A lexical head combines with its complements and subject or specifier (if any) according to the lexically inherited specification, as shown in (1).