Contents

 
Figures xi
Tables xv
Preface xvii
Acknowledgements xix
1 Introduction 1
1.1 Motivation 1
1.2 Overview of the book 6
1.3 Rhetorical Organization of the Book 8
I Theoretical Foundations 11
Preamble 13
2 The Linguistics of Text Structures 15
2.1 Towards Formalizing the Structure of Free, Unrestricted Texts 15
2.2 Rhetorical Structure Theory 19
2.3 The Formulation of a Compositionality Criterion of Valid Text Structures 25
2.4 From Texts to Discourse Structures 33
3 The Mathematics of Text Structures 39
3.1 A Model-Theoretic Account of Valid Text Structures 39
3.2 A Proof-Theoretic Account of Valid Text Structures 52
3.3 The Relation between the Axiomatization of Valid Text Structures and Its Proof Theory 63
4  A Computational Account of the Axiomatization of Valid Text Structures and its Proof Theory 69
4.1 Introduction 69
4.2 Deriving Text Structures - A Constraint-Satisfaction Approach 69
4.3 Deriving Text Structures - A Propositional Logic, Satisfiability Approach 70
4.4 Deriving Text Structures - A Proof Theoretic Approach 71
4.5 Implementation and Empirical Results 72
4.6 Applications 75
5 Discussion 77
5.1 Related Work 77
5.2 Open Problems 81
5.3 Summary 82
II The Rhetorical Parsing of Free Texts 85
Preamble 87
6 Rhetorical Parsing by Means of Manually Derived Rules 91
6.1 Arguments for a Shallow, Cue-Phrase-Based Approach to Rhetorical Parsing 91
6.2 A Corpus Analysis of Cue Phrases 97
6.3 A Cue-Phrase-Based Approach to Rhetorical Parsing 109
7 Rhetorical Parsing by Means of Automatically Derived Rules 149
7.1 Introduction 149
7.2 A Corpus Analysis of Discourse Trees 149
7.3 A Decision Tee-Based Approach to Rhetorical Parsing 152
8 Discussion 173
8.1 Related Work 173
8.2 Open Problems 178
8.3 Summary 183
III Summarization 185
Preamble 187
9 Summarizing Natural Language Texts 189
9.1 From Discourse Structures to Text Summaries 189
9.2 Evaluation of the Rhetorical-Based Approach to Summarization 193
10 Improving Summarization Performance through Rhetorical Parsing Tuning 203
10.1 Motivation 203
10.2 An Enhanced Discourse-Based Framework for Text Summarization 204
10.3 Combining Heuristics 207
10.4 Learning the Best Combinations of Heuristics 212
11 Discussion 219
11.1 Related Work 219
11.2 Open Problems 220
11.3 Other Applications 225
11.4 Summary 228
Bibliography 229
Author Index 243
Subject and Notation Index 247