What’s New?

1. What’s New? Discourse & Dialogue CMSC 35900-1 October 28, 2004

2. Agenda • Attention and Information • Given/New dichotomy • Implications & Applications • Given/New-based paraphrase • Speech recognition & synthesis • Stress and accent • Gestural synthesis

3. Discourse • So far • Analytic models (G&S,M&T) • Discourse structure recognition, segmentation • Now, generation and synthesis • Sentence/paragraph surface realization • Grammatical forms of discourse entities – pron, def NP • Sentence ordering of information – subj/not • Acoustic form of entities- accented/not; accent type

4. Attention and Information • Perspective: Focus of Attention • Coherence, Reference • Perspective: Information Flow • Goal of discourse: • Communication of information • Speaker to hearer

5. Given/New Dichotomy • Each “information unit” contains • “New” information • the “News” • New to hearer • New to discourse • “Given/Old” information • What is being talked about • Known to hearer • Already evoked in discourse

6. Given/New Effects • Influences structure of utterance • Word order • Form of referring expression • Prosodic prominence • Guides interpretation by hearer

7. Given/New & Word Order • Default word order (English, declarative) • Left-to-right increase in “New-ness” • Subject -> Given • Discourse-old - present in context • Predicate -> New

8. Given/New & Referring Expressions • Hierarchy of salience • Tied to Given/New status • Given+Salient -> Pronoun • Given, less salient -> Definite NP • New -> Indefinite NP

9. Given/New & Prosody • Prosody • Pitch, Loudness, Duration, … • Tone group = Information Unit • Given + New • Unstressed -> Given, salient • Stressed -> New, less salient

10. Application of Information Flow • Paraphrase (McKeown 1983) • Natural language is ambiguous • Semantic - word senses - e.g. bank • Syntactic - structural • E.g. prepositional phrase attachment • Reference… • Paraphrase makes explicit system interpretation • Especially modification

11. Given/New Perspective • Word order affected by role in sentence • What speaker thinks hearer knows or not • Wh-items are “new”, rest “given”, assume true • Question: 3 parts • 2:Lack of knowledge: wh-item with no subclause • 3:Angle: Direct/Indirect modifiers of wh-items • 1:Given info: Everything else

12. Example • Q: Which active users advised by Tom Wirth work on projects in area 3? • P: Assuming that there are projects in area 3, which active users work on those projects? Look for users advised by Wirth. New: lack info Work on Active users projects New: Angle Advised by TW Given In area 3

13. Syntax & Information Structure • Link parse tree to Given/new info • Root = Main verb = Inorder traversal • Left subtree= Subject = Preorder • Right subtree = Object = Preorder • Traversal order + Part information+Transform • > Linearization

14. Paraphrase by Given/New • Advantages: • Corrective response: e.g. if given info isn’t • More flexible/portable that template-based paraphrase

15. Applications of Info Structure • Speech recognition and synthesis • Prosody • Pitch, loudness, length • New - more likely stressed; Old: often unstressed • “Tunes” for given/new

16. Understanding Acoustic Realization • Motivation • Synthetic speech • Experimental evidence • Key components • Prosody • Syntax • Contextually “appropriate” speech synthesis

17. Speech Synthesis • Generally INTELLIGIBLE • But not NATURAL • Requires high attention to listen to • “Default” sentence intonation • May be misleading • Speaking of BILL, • A) JOHN thought he would WIN, but he DIDN’T • B) JOHN thought he would WIN, but HE didn’t

18. Accent Assignment: Analysis • Accent: • Increased loudness, duration, pitch movement • Basic view: • “available”/Given: no accent; New(er): accent • Attend to new information • Questions: • Does accent continue to decrease with repetition? • How does discourse “structure” affect accent?

19. Accent Assignment: Results • “Topic” status & First/Later mention vs • De-/Accenting, form of referring expression • Results: • First,+Topic: Accented, Full NP • Later,+Topic: De-accented , probably pronoun • Later,+Topic,+Refinement: Accented (even Pron) • First,-Topic: Accented Full NP • Later,-Topic: Accented Full NP, Implicit • Later,-Topic,+past-topic/+contrast: Accented NP (mod)

20. “ToBI” Intonation Framework • ToBI: Tone and Break Indices • Describe English sentence intonation • Tones: • Two pitch levels: H(igh) and L(ow) • * - on stressed syllable, e.g. H*, L*, L+H* • Types: Pitch accents, Phrase Tones (L-,L%) • Last accent in phrase = ‘nuclear’ accent • Units: Intermediate and Intonational Phrases

21. “ToBI” Intonation Framework • Break indices • Mark groupings in speech • 0 - most closely linked; 5 - most disjoint • 4 = Intermediate phrase boundary (-) • ~ comma • 5 = Intonational phrase boundary (%,$) • ~ period - sentence

22. ToBI Examples

23. Contrast Examples

24. Contrast Examples

25. Contrast Examples

26. Syntax & Information Status • Intonation units more flexible than standard syntactic constituents, e.g. subject, predicate • CCG - Combinatory Categorial Grammar • Allows multiple analyses (parses) to fit • Link syntactic, semantic, and pragmatic/prosodic function with each unit

27. Generating Appropriate Intonation • Basic “previous mention” strategy • Accent first mention of content words • De-accent closed class function words • De-accent content words already mentioned • Inadequate • Need contrastive stress TOO

28. Generating Appropriate Intonation • Identify theme (topic: links to previous info) • Identify rheme (contributes new information) • Shared propositional content • Assign appropriate basic intonation contour • rheme:H* L-L%; • theme:L+H* L-H% (at most)

29. Generating Appropriate Intonation • Identify focus element in theme/rheme • Word to get accent • Focus • First mention, and • Contrastive • What is contrastive????

30. Contrastive Items: Domain • For each entity x: • 0: find alternatives in discourse and KB • 1: RSET= x and alternatives, • PROPS= features of x • CSET= features of x to mark for contrast • 2: For each p in PROPS, r in RSET, • IF p is not property of r, add p to CSET. • 3: Focus p of x • E.g. She broke her left LEG, NOT her RIGHT leg.

31. Contrastive Items: WordNet • WordNet: Semantic KB • 4 parts of speech: N,V,Adj, Adv • Category/word: one or more synonym sets • Hierarchies linked by relations: e.g. IS-A • Content Word W is new if NOT: • In focus history or history’s equivalence class • Equiv. Class: reachable by N hypernym/synset links • Content Word W is contrastive if: • In history’s contrast list • Contrast: hyponyms of hypernyms of W

32. Examples • (84) Q: I know which AMPLIFIER produces clean BASS, • but WHICH amplifier produces clean TREBLE? • L+H* L(H%) H* LL$ • A: The BRITISH amplifier produces clean TREBLE. • H* L(L%) L+H* LH$ • (85) Q: I know which AMPLIFIER produces MUDDY treble, • but WHICH amplifier produces CLEAN treble? • L+H* L(H%) H* LL$ • A: The BRITISH amplifier produces CLEAN treble. • H* L(L%) L+H* LH$

33. Summary • Assigns contextually based intonation • Uses given/new information status • Extended to fine-grained contrastive status • Identifies contrast based on • Knowledge base if available • WordNet Lexical DB for greater generality

34. Conclusions • Theme/Rheme identification difficult • Contrast/Similarity measures for WordNet • Still oversimplified • Evaluation: How do you tell if it’s right? • Many alternatives • Incorporate in larger discourse structure • Discourse segments, plans, ….

35. Examples • The X4 is a SOLID-state AMPLIFIER • L+H*L- H* H* L- L$ • The X5 is a TUBE amplifier. • L+H*L- H* L-L$ • It COSTS EIGHT HUNDRED DOLLARS, • H* H* H* H* L-H% • IT costs NINE hundred dollars, • L+H*L- H* L-H%