This thesis has been submitted in fulfilment of the requirements for a postgraduate degree

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THE FORMALISATION OF DISCOURSE PRODUCTION
by
Anthony Davey
Ph.D University of Edinburgh 1974
ABSTRACT
This paper describes a computer program which produces English
discourse. The program is capable of describing in a sequence of
English sentences any game of noughts-&-crosses (tic-tac-toe), whether
given or actually played with the program. The object is to understand
something of what a speaker is doing when he speaks, and the program
therefore demonstrates the operation of rules for selecting information
into sentences, for connecting sentences into a discourse, and for
constructing clauses, groups, and v.ords to convey the required
information with the rnaxnnwm possible economy.
The program uses a systEmic functional grarrrnar to co-operate with
semantic procedures in producing English. The gramnar generates only
a range of English, but one which is nonetheless sufficient to
l~ited
illustrate the advantages both theoretical and practical of such a
grammar for a productive system.
Many other computer programs have accepted more or less natural
English input, usually in the form of questions requiring an answer,
but few have been designed to produce natural English, particularly
connected discourse. As a producing system the present model offers
a view of language use from a viewpoint slightly different from that
of its predecessorso However comprehension and production are
dependent on each other, so that study of one may be expected to
illuminate the other.
CONTENTS
1 INTRODUCTION 1
2 GAME DESCRIPTIONS 15
2.1 Introduction 15
2.2 Planning Discourse 15
2.3 Sentence Organisation 22
2.3.1 Verb, and sentence structure 23
2.3.2 Verb selection 25
2.4 Referring expressions 26
2.4.1 Context and implicit antecedents 26
2.4.2 Pronouns 28
2.4.3 Non-pronoun referring expressions 31
2.5 Examples 33
3 A REVIEW OF PREVIOUS SYSTEMS 38
3.1 Introduction 38
3.2 The understanding hearer 38
3.2.1 Fixed-format systems 40
3.2.2 Text-based systems 43
3.2.3 Limited deductive systems 44
3.2.4 General deductive systems 49
3.2.5 Other projects 53
3.3 Local context 56
3.3.1 Sub-contexts 56
3.3.2 Anaphora 57
3.3.2.1 Pronouns in Winograd's
system 59
3.3.3 Partial utterance 62
3.4 Syntax 63
3.4.1 Systemic grammar in SHRDLU 65
3.4.2 Augmented transition networks 67
4 A SYSTEMIC FUNCTIONAL GRAMMAR 70
4.1 Systemic functional grammar 70
4.1.1 Introduction 70
4.1.2 Overview and examples 70b
4.1.3 Grammatical items 75
4.1.4 Features and systems 77
4.2 The scope of the program's grammar 80
4.3 The {TYPE} system 81
4.4 The clause systems 81
4.4.1 {TRANSITIVITY} systems 82
4.4.2 {MOOD} systems 85
4.4.3 {ASPECT} systems 90
4.4.4 {UNDERSTANDING} systems 91
4.4.4.1 Introduction 91
4.4.4.2 What an {Understanding}
item understands 95
4.4.4.3 Accounting for understanding 97
4.4.4.4 Alternative accounts 102
4.4.5 {ADJUNCT} systems 108
4.4.6 Clause systems: the unified net\\Ork 112a
4.5 The Group systems 113
4.5.1 Verb-group systems 114
4.5.2 Noun-group systems 117
4.5.3 Preposition-group systems 136
4.5.4 Adjective-group systems 138
4.6 Word systems 142
4.7 {COORDINATION} systems 143
5 THE FUNCTIONS IN THE GRAMMAR 151
5.1 Introduction 151
5.2 Functions 152
5.3 Realisation relations 156
5.4 Structure-building rules 159
5.5 Clause rules 162
5.5.1 The Clause Feature-Realisation rules 162
5.5.2 The Clause Structure-Building rules 164
5.5.3 The Clause FUnction-Realisation rules 165
5.5.4 Notes on clause rules 166
5.5.5 Two worked examples 169
5.6 Verb-groups 175
5.7 Noun-group rules 175
5.7.1 Noun-group Feature-Realisation rules 175
5.7.2 Noun-group Structure-Building rules 176i
5.7.3 Noun-group FUnction-Realisation rules 176ii
5.7.4 Notes on the noun-group rules 177
5.7.5 Examples 180
5.8 Preposition-group rules 183
5.8.1 Preposition-group realisation
and building rules 183
5.8.2 Notes on the rules and an example 184
5.9 Adjective-group rules 184
5.10 Doing without functions 186
6 A DESCRIPTION OF THE PROGRAM 194
6.1 Introduction 194
6.2 An outline of the program 195
6.3 Designing a sentence 200
6.3.1 A detailed description of the
design procedures 200
6.3.2 On being surprised, sequence
and contrast 207
6.3.3 Mentioning mistakes 215
6.4 The construction procedures - Introduction 217
6.5 Making clauses 220
6.6 Making verb-groups 229
6.7 Making noun-groups 230
6.7.1 Overview 230
6.7.2 The criterion of adequacy 231
6.7.3 Finding an adequate referring expression 233
6.7.4 The concept of definiteness 237
6.7.5 Coordination and the referent
equivalence class 241
6.7.6 Proref and prostring pronoun 242
6.7.7 The restriction-finding specialist 257
6.7.7.1 Introduction 257
6.7.7.2 The anaphoric adjective
'other' 259
6.7.7.3 Implicit antecedents 265
6.7.7.4 The anaphoric adjective
'same' 266
6.8 Making preposition-groups 268
6.9 Making adjective-groups 273
6.10 Making words 273
APPENDIX 1 Original examples of output 282
Example 1 A game is played and described 282
Example 2 A game is given and described 283
Example 3 Three short examples showing anaphora 284
Example 4 Three short examples 285
Example 5 The constituent structure of a
noun-group displayed as a tree 286
APPENDIX 2 A worked example of sentence production 287
APPENDIX 3 The program 288
Directory of functions within files 288
Files in alphabetical order of title:
BFETCH 289
BOARD 290
CHECKMEN 291
CLAUSE FUNCTION FNS 293
CLAUSE RULES 294
CONJUNCT TABLE 297
DESIGNO 298
DESIGN1 299
DE TERM IN 302
ENTITY 303
EQCL 304
FTR FNS 305
GAMEFNS 308
HCLHFNS 309
LOCDESCR 311
LOCDESCR FNS 313
LOCDESCR FNS 2 317
LOCDlO 320
LOCFNS 322
LRRP 324
MACROS 326
MAKEADJG 327
MAKENG 328
MAKEPNG 331
MAKERELN 332
MAKES 333
MAKESFN1 336
MAKES IF 337
MAKEVG 338
MAKEWORD 339
NFEATFNS 340
NGFNS 341
NGRULES 343
ODDFNS 345
ODDFNS2 346
ODDFNS4 347
PREPG RULES 348
RDMOVES 349
SB FNS 350
SETFNS 352
SET UP 354
SPIELEN 355
SUFFIX 358
TREE DISPLAY FNS 359
TREEFNS 361
SPATREL 363
SPOUT 364
UPDATE1 366
VG FNS 367
V SETUP 368
REFERENCES
390