generalized phrase-structure grammar (GPSG)

A LINGUISTIC theory which was developed as an alternative to TRANSFORMATIONAL accounts of language. GPSGs are weakly equivalent to a class of context-free phrase-structure grammars (PSGs). In GPSG, there are no transformations, and the SYNTACTIC structure of a SENTENCE is a single PHRASE-MARKER. Also, in traditional PSG, CATEGORY LABELS (e.g. NP, S) have no internal structure, whereas in GPSG a category is a set of FEATURE specifications (ordered pairs containing a feature and a feature value) which RULES can access. Instead of phrase-structure rules, GPSGs employ separate immediate DOMINANCE and linear PRECEDENCE rules. These interact with various general principles, feature CO-OCCURRENCE restrictions, and feature specification defaults to determine what local TREES (i.e. trees consisting of a NODE and its DAUGHTER or daughters) are well formed. This approach allows several generalizations to be captured in a way that is not possible with phrasestructure rules. GPSGs also employ METARULES, which derive immediate dominance rules from immediate dominance rules. An important offshoot of GPSG is HEAD-DRIVEN PHRASE-STRUCTURE GRAMMAR. A further generalization of this approach has been called generalized generalized phrase-structure grammar (G² PSG), in which the HEAD-feature convention, the FOOT feature principle, the CONTROL AGREEMENT PRINCIPLE, and the system of feature specification DEFAULTS are subsumed into a single mechanism – an extension of the feature co-occurrence restriction mechanism of standard GPSG.