This thesis is concerned with a presentation of Classification -based Phrase Structure
Grammar (or cPSG), a grammatical theory that has grown out of extensive revisions
of, and extensions to, HPSG. The fundamental difference between this theory and HPSG
concerns the central role that classification plays in the grammar: the grammar classifies
strings, according to their feature structure descriptions, as being of various types.
Apart from the role of classification, the theory bears a close resemblance to HPSG,
though it is by no means a direct translation, including numerous revisions and extensions.
A central goal in the development of the theory has been its computational
implementation, which is included in the thesis.
The presentation may be divided into four parts. In the first, chapters 1 and 2, we
present the grammatical formalism within which the theory is stated. This consists of a
development of the notion of a classificatory system (chapter 1), and the incorporation
of hierarchality into that notion (chapter 2).
The second part concerns syntactic issues. Chapter 3 revises the HPSG treatment of
specifiers, complements and adjuncts, incorporating ideas that specifiers and complements
should be distinguished and presenting a treatment of adjuncts whereby the
head is selected for by the adjunct. Chapter 4 presents several options for an account of
unbounded dependencies. The accounts are based loosely on that of GPSG, and a reconstruction
of GPSG's Foot Feature Principle is presented which does not involve a notion
of default. Chapter 5 discusses coordination, employing an extension of Rounds- Kasper
logic to allow a treatment of cross -categorial coordination.
In the third part, chapters 6, 7 and 8, we turn to semantic issues. We begin (Chapter 6)
with a discussion of Situation Theory, the background semantic theory, attempting to
establish a precise and coherent version of the theory within which to work. Chapter 7
presents the bulk of the treatment of semantics, and can be seen as an extensive revision
of the HPSG treatment of semantics. The aim is to provide a semantic treatment which
is faithful to the version of Situation Theory presented in Chapter 6. Chapter 8 deals
with quantification, discussing the nature of quantification in Situation Theory before
presenting a treatment of quantification in CPSG. Some residual questions about the
semantics of coordinated noun phrases are also addressed in this chapter.
The final part, Chapter 9, concerns the actual computational implementation of the
theory. A parsing algorithm based on hierarchical classification is presented, along with
four strategies that might be adopted given that algorithm. Also discussed are some
implementation details. A concluding chapter summarises the arguments of the thesis
and outlines some avenues for future research.