Phrase Structure Rules

Introduction

X-Bar Rules

Head Movement Rules

GLR Machine

Introduction

The phrase structure of a language L is defined in two files. The first one, called xbar.pl by convention, defines common rules. The second, called peripheryL, contains rules particular to language L:

xbar.pl General phrase structure rules such as X-bar and adjunction rules. Basic rules for empty categories plus head movement.

peripheryL.pl Phrase structure rules particular to language L.

At compile time, these two files are automatically concatenated into a single file:

xbarperipheryL.pl Phrase structure rules for language L.

This is done before any processing occurs. Hence, care must be taken not to multiply define rules.

Phrase structure (PS) rules defined in these two files are not directly used to parse sentences. Instead, they are compiled into a language-specific GLR machine for efficient, bottom-up parsing. More precisely, they undergo a (simplified) two-stage process:

xbarperipheryL.pl

rule/4 Compiler

ssrules
rule(LHS,RHS,Gs,Inh) facts

GLR Compiler

GLR Transition Table
transition(S₁,V_N,S₂) facts GLR Action Table
action(S,V_T,CF,CF') rules

(a) Two-step PS rule compilation process

In the following sections, we will first document the PS rules available to the user.

X-rules

X-rules are rules with symbol variables, not ground symbols. These are used to encode families of phrase structure rules.

Head Movement Rules

References: Implementation Notes

GLR Machine