1 Discourse Coherence Lecture Plan: Einf¨ uhrung in Pragmatik • Discourse cohesion and coherence • Coherence relations und Texttheorie • Sources of discourse structure • Discourse Structure Theory (Grosz&Sidner’86) Discourse Coherence – intentional structure – attentional structure – linguistic structure Ivana Kruij ff -Korbayov´ a • Rhetorical Structure Theory (Mann and Thompson 1987) korbay@coli.uni-sb.de Reading: Jurafsky et al. 2000 [Chapter 16] http://www.coli.uni-sb.de/cl/courses/PTT/ Grosz et al. 1990; Grosz and Sidner 1986; Hobbs 1979, 1985; Mann and Summer Semester 2004 Thompson 1987 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 2 3 Motivation Motivation (1) a. John hid Bill’s car keys. (3) a. John can open Bill’s safe. b. He was drunk. b. He knows the combination. (4) a. Bill is worried because his safe can be opened by John. (2) a. John took the train from Paris to Istanbul. b. He knows the combination. b. He likes spinach. I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04
4 5 What constitutes a discourse? Discourse Coherence and Cohesion Parts of discourse are tied together: • Units of language and language use, consisting of more than a single utterance. Cohesion non-structural text-forming relations, e.g., reference (esp. anaphora), • More than an arbitrary collection/sequence of well-formed utterances. ellipsis, conjunction, lexical cohesion. The interpretation of elements is inter- dependent. • Connected in some way, e.g. by Coherence structural relations between elements/segments of discourse, – some system of related topics involving functional predicate-argument or modification relations, e.g., – coherence of events in the world/situation explanation, result, justification, etc. – a need to relate what has been said to some goal of communication What mechanisms make certain sequences of utterances (more) coherent and (5) John hid Bill’s car keys. He was drunk. cohesive? (6) John hid Bill’s car keys. Whales are mammals. I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 6 7 Discourse Coherence Discourse Relations: Example A coherent discourse consists of discourse units (segments) connected by discourse (7) A: relations (coherence relations). a. John went to jail. b. He was caught embezzling funds from the pension plan. Explanation ∀ w, e Sentence ( w, e ) ⇒ Segment ( w, e ) B: ∀ w 1 , w 2 , e 1 , e 2 , e a. Yes, John was caught embezzling funds. Segment ( w 1 , e 1 ) ∧ Segment ( w 2 , e 2 ) ∧ CoherenceRel ( e 1 , e 2 , e ) ⇒ Segment ( w 1 , w 2 , e ) b. But he went to jail To interpret a coherent discourse W , we must prove that it is a segment: c. because he was convicted of tax fraud. ∃ e Segment ( W, e ) The meaning of a discourse is more than the summ of its parts: Discourse relations are semantic predicates that take other bits of propositional content as arguments. They add semantic content. I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04
8 9 Discourse Connectives B’: a. No, that’s not right. Discourse relations can be implicit or explicitly signaled by discourse connectives. Discourse connectives are linguistic means to express (or at least signal or b. Although John was caught embezzling funds, constrain) cherence relations between discourse segments. c. he went to jail d. because he was convicted of tax fraud. (8) On the one hand, John is very generous. For example, if you need money, you only have to ask him for it. On the other hand, he is very hard to find. (9) John loves barollo. So he ordered three cases of the ’97. But then he had to cancel the order, because he discovered he was broke. I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 10 11 Arguments of Discourse Relations Discourse Relations and Anaphora Individual anaphora (10) a. One plainti ff had never received full pay. b. He had also been passed over for promotion three times. (13) John can open Bill’s safe. He knows the combination. c. Moreover, he had been denied a job because of his race. (14) John hid Bill’s car keys. He was drunk. d. Nevertheless he had never filed a complaint until now. (15) a. The police prohibited the women from demonstrating. (11) a. One plainti ff had never received full pay. b. They feared violence. b. He had also been passed over for promotion three times. c. Moreover, he had been denied a job because of his race. Tense/Aspect/Mood dependencies : d. Nevertheless he had never filed a complaint until now. (16) Peter fell. Max kicked him. (12) If the light is red, stop. (17) Peter fell. Max pushed him. a. Otherwise you might get run over. (18) Peter fell. Max had pushed him. b. Otherwise you can go straight on. I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04
12 13 Discourse Segmentation and Anaphora Sources of Discourse Structure (19) a. One plainti ff had never received full pay. • Discourse participants are embodied in a domain , which has its own internal b. Another had been passed over for promotion three times. structure. The speaker/hearer are aware of the domain structure, and use it c. Yet another had been denied a job because of his race. this knowledge to produce/interpret the discourse. d. But the jury didn’t believe this . • Discourse participants have intentions : They are engaged in tasks and have (20) a. One plainti ff had never received full pay. communicative goals. Speaker wants to communicate something to the b. Another had been passed over for promotion three times. hearer, she wants the hearer to recognize her communicative purpose(s) , c. Yet another had been denied a job because of his race. such making H believe p , making H adopt some action/plan. d. These people were really badly treated. e. But the jury didn’t believe this . • Discourse participants have limited resources : Both speaker and hearer only have limited short-term memory, and therefore there are limits to what they can recover from what has been previously said; however, this may not be a purely sequential matter, hierarchical organization seems to play a role. I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 14 15 Sources of Discourse Structure Sources of Discourse Structure (21) A. Can you please describe your house? (22) . . . Melt the butter in a large pan and add the vegetables; B. . . . then in the kitchen . . . there’s a large window which faces the saute them for 7-8 minutes, backyard with two smaller windows directly flanking it and . . . if we’re but don’t let them brown, facing . . . towards the backyard now on the righthand side is . . . a sliding then add the butter beans, glass door and a small window . . . on the left is a stove and a refrigerator water or stock, . . . the milk and the bouquet garni. Simmer gently, with lid half on the saucepan, for about 1.25 hours, or until the butter beans are tender. . . . Reheat the soup, but don’t let it boil. I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04
16 17 Sources of Discourse Structure Sources of Discourse Structure (Uttered on April 10th) (23) E. Good morning. I would like for you to re-assemble the compressor. . . . (24) A. Let’s have the one-day workshop in July. E. I suggest you begin by attaching the pump to the platform. B. OK. (other subtasks) B. Are you available on the 15th? E. Good. All that remains then is to attach the belt housing cover to A. I’m afraid not. But I am free on the 17th. the belt housing frame. B. OK. Let’s meet at 10 a.m. A. All right. B. How about the HCRC seminar room? I assume the belt housing cover opens to the pump pulley rather A. It’s not available on the 17th. than to the motor pulley. B. So let’s meet in 6BP. E. Yes, that is correct. . . . A. All right, the belt housing cover is on and tightened down. E. Fine. Now, let’s see if it works. I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 18 19 Approaches to Discourse Discourse Structure Theory (Grosz and Sidner 1986) • resolution of anaphoric reference: various approaches to restricting the search space, i.e., non-linear precedence and heuristics Three inter-related and co-constraining aspects of discourse structure: Linguistic: discourse segments and their relations (e.g., embedding) are signalled • determination of discourse structure: theories of discourse structure postulate in the linguistic form of expressions: cue phrases, intonation, etc. di ff erent types of information as central to the computation of discourse structure. Attentional: at every point in the discourse, a set of entities is salient (i.e., in – a notion of discourse grammar analogous to sentence grammar the center of attention); there are transitions between attentional states – recognition of communicative intentions using a set of coherence/rhetorical relations Intentional: each discourse segment has a unique purpose (DSP); there are – planning & action relations between DSPs (satisfaction-precedence vs. dominance) – inference based on domain-specific or commonsense knowledge I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04 I.Kruij ff -Korbayov´ a Discourse Coherence PTT:SS04
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