Discourse and Inference Jerry R. Hobbs Artificial Intelligence Center SRI International Menlo Park, California January 8, 2004 2 Contents 4Syntax 5 4.1RoleofSyntax.......................... 5 4.1.1 SyntaxastheInterpretationofProximity....... 5 4.1.2 TheFociofThisChapter................ 7 4.1.3 Influences and Allegiances ................ 8 4.2 The Structure of Syn ...................... 9 4.2.1 Concatenation...................... 9 4.2.2 ArgumentsofPredicates................. 11 4.2.3 Agreement........................ 15 4.2.4 Gaps............................ 21 4.2.5 Summary......................... 23 4.3LexicalAxioms.......................... 24 4.4TheBasicClause-LevelCompositionRules.......... 26 4.5Clause-LevelPhenomena..................... 30 4.5.1 Moods........................... 30 4.5.2 OnWhatisSaidandPresuppositions......... 33 4.5.3 LexicalSentences..................... 37 4.6VerbPhraseRules........................ 38 4.6.1 VerbMorphology..................... 38 4.6.2 Intransitives,Transitives,andDitransitives...... 43 4.6.3 PrepositionalArguments................ 47 4.6.4 SeparableParticles.................... 52 4.6.5 SententialComplements................. 53 4.6.6 SubjectandObjectControlVerbs........... 55 4.6.7 Auxilliaries . ....................... 58 4.7PredicateComplements..................... 64 4.7.1 TheCopula........................ 64 4.7.2 Adjectival Complements . ................ 68 4.7.3 ToughMovement..................... 75 3 4 CONTENTS 4.7.4 Passives.......................... 78 4.7.5 Prepositions and Subordinate Conjunctions . 80 4.7.6 Progressives........................ 82 4.8SmallClauses........................... 83 4.9Adjuncts.............................. 87 4.9.1 AdjunctPlacement.................... 87 4.9.2 PredicateComplementsasAdjuncts.......... 90 4.9.3 Adverbs.......................... 92 4.9.4 Purpose Infinitives . .................. 96 4.9.5 TimeandMeasureNPs................. 96 4.9.6 Separators......................... 97 4.10NounPhraseRules........................ 99 4.10.1TheStructureoftheNounPhrase........... 99 4.10.2NounMorphology....................108 4.10.3LexicalAxiomsforNouns................109 4.10.4 Proper Noun Phrases and Personal Pronouns . 117 4.10.5HeadlessNounPhrases.................118 4.10.6 The Adjective Position ..................119 4.10.7 Inflectional and Derivational Adjective Morphology . 126 4.10.8 Determiner Phrases . ..................128 4.10.9IndefinitePronouns...................139 4.10.10Numbers.........................141 4.10.11Case,Gender,Person,andNumber...........144 4.10.12 A Word on X Theory..................150 4.11ReflexivePronouns........................151 4.12IntensiveReflexives........................152 4.13Long-DistanceDependencies...................152 4.13.1Overview.........................152 4.13.2IntroducingGaps.....................153 4.13.3TheStructureofRelativizers..............156 4.13.4 Composing Relativizers and Matrix Clauses . 163 4.13.5“That”..........................169 4.13.6 Some Other Long-Distance Dependency Constructions 172 4.14Conjunction............................173 4.14.1ConjunctionofLikeConstituents............173 4.14.2 Ellipsis . .........................176 4.14.3Gapping..........................177 4.14.4OtherConjunctionPhenomena.............178 4.15Comparatives...........................180 4.15.1Overview.........................180 CONTENTS 5 4.15.2“More”..........................183 4.15.3“Than”..........................184 4.15.4PlayingtheSameRole..................187 4.15.5SomeExamplesAnalyzed................195 4.15.6ComparativesandSuperlatives.............208 4.16SummaryofGrammar......................208 4.16.1Overview.........................208 4.16.2CompositionRules....................210 4.16.3AlternationAxioms...................215 4.16.4LexicalAxioms......................217 4.16.5AgreementFeatures...................220 4.17 Some Problems Analyzed as Metonymy . ......224 4.17.1 The Basic Axioms of Metonymy . ......224 4.17.2ExtraposedModifiers..................229 4.17.3Ataxis...........................232 4.17.4 Distributive and Collective Readings . ......233 4.17.5 Asserting Grammatically Subordinated Information . 236 4.17.6MonotoneDecreasingQuantifiers............238 4.18 Performing with Competence . ................239 4.18.1TheDataandtheAnalysis...............239 4.18.2ElementaryOperations.................255 4.19TheEdgesofSyntax.......................255 4.19.1LanguageandProtolanguage..............255 4.19.2Fragments:ATelegraphicMessage...........258 4.19.3Scrambling:ASonnet..................263 4.19.4 Disfluencies: A Transcript of a Meeting . ......266 4.19.5Co-Construction.....................272 4.19.6 The FASTIAN Bargain: Skimming, or Language as Protolanguage......................273 4.20TheEvolutionofSyntax.....................273 4.21Modularity............................279 6 CONTENTS Chapter 4 The Syntax of English in an Abductive Framework 4.1 The Role of Syntax in a Theory of Interpreta- tion 4.1.1 Syntax as the Interpretation of Proximity To understand our environment we seek the best explanation for the ob- servable features we find there. Among the observable features that we seek to explain are proximities among objects. This generally escapes our notice except when it is out of the ordinary, as when we see a chair on top of a table or a dog in the aisle of a theatre. When things are in their place, the explanation is that that is their place. A similar problem faces us in discourse. A text is a string of words, and one of the features of the text that requires explanation is the adjacency of pairs of words or larger segments of text. The simplest example of this is provided by compound nominals. When we see the phrase “turpentine jar” in a text, the interpretation problem we face is finding the most reasonable relationship in the context between turpentine and jars, using what we know about turpentine and jars. In many compound nominals, the relationship is one conveyed by one of the nouns itself. In “virus replication”, the relation between the virus and the replication is precisely the “replication” relation—it is the virus that is replicating. Syntax and compositional semantics can be seen as arising out of this need to explain adjacency. When we see the pair of words “men work”, 7 8 CHAPTER 4. SYNTAX we need to find some relation between them. The second word itself pro- vides the relation. It is the men who are working. Whereas in the case of “virus replication”, “replication” provides a possible relation, in the case of “men work”, “work” provides an obligatory relation. (This is not quite true; metonymy is possible, so that the second word need only provide a relation between the eventuality it denotes and something functionally related to the the first word, as in “The office called.”) The hypothesis that sentences have syntactic structure amounts to the acceptance of a set of constraints on the relations that can obtain be- tween two words or larger stretches of text, restricting these relations to be predicate-argument relations (plus metonymy). The tree structure of sentences arises from the fact that the adjacency relation can be between larger segments of text than simply single words, where the segments have their own internal tree structure resulting from adjacencies. For example, in John believes men work. we don’t seek to explain the adjacency between “believes” and “men”. Rather we first explain the adjacency between “men” and “work”, and only then the adjacency between “believes” and “men work” (or the adjacency among “John”, “believes”, and “men work”, depending on your view of the structure of the clause.) This kind of grouping occurs even in the absence of syntactic constraints. Consider the two compound nominals, “Stanford Research Institute” and “Cancer Research Institute”. In the latter, we must first find the relationship between cancer and research, and then find the re- lationship between cancer research and the institute, whereas in the former, we group “Research” with “Institute” and then “Stanford” with “Research Institute”. When a predicate-argument relation is found between adjacent segments, the two together constitute a single segment. Different types of composi- tions yield different types of segments. “Men work” and “tall men” both encode predicate-argument relations, but one is a sentence (S) and the other a noun phrase (NP). The intermediate structures in the syntactic analysis of a sentence—verb phrases (VP), prepositional phrases (PP), and so on— represent different ways in which the recognition of a predicate-argument relation results in the composition of two segments into a single larger seg- ment. In order to recognize predicate-argument relations between segments of text larger than one word, we need to know what predicates or arguments are conveyed by the segments. For example, “research institute” refers to 4.1. ROLE OF SYNTAX 9 an institute rather than research. If this segment provides the argument in larger composed segment, the institute and not the research will be the argument. Similarly, “men work” describes a working event rather than a condition of being men. If we compose it with “today”, it is the working that is today. As we compose larger and larger segments of text, we must be able to specify the primary information conveyed by the composite segments. The rules of syntax and compositional semantics specify how segments of text can be grouped together, what types of segments result from the grouping, and what the primary information