Generalised phrase structure grammar (GPSG) is
a framework for describing the syntax
of natural languages. GPSG was initially developed in
the late 1970s by Gerald
Gazdar. Other contributors include Ewan
Sag, and Geoffrey
Pullum. Their book Generalized Phrase Structure
Grammar, published in 1985, is the main monograph
on GPSG, especially as it applies to English syntax.
One of the chief goals of GPSG is to show that the syntax
of natural languages can be described by context-free
grammars (CFGs), with some suitable conventions intended
to make writing such grammars easier for syntacticians.
Among these conventions are a sophisticated feature
structure system and so-called "meta-rules", which
are rules generating the productions of a context-free
grammar. GPSG further augments syntactic descriptions
with semantic annotations that can be used to compute
the compositional meaning of a sentence from its syntactic
derivation tree. However, it has been argued (for example
Berwick) that these extensions require parsing
algorithms of a higher order of computational
complexity than those used for basic CFGs.
Gerald Gazdar, and many other syntacticians, have since
argued that natural languages cannot in fact be adequately
described by CFGs .
GPSG is in part a reaction against transformational
theories of syntax. In fact, the notational extensions
to context-free grammars developed in GPSG are claimed
to make transformations redundant. Most of the syntactic
innovations of GPSG were subsequently incorporated into
phrase structure grammar.
Gerald; Ewan H. Klein, Geoffrey K. Pullum, Ivan A. Sag
(1985). Generalized Phrase Structure Grammar.
Oxford: Blackwell, and Cambridge, MA: Harvard University