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Prosody & Information Structure

Prosody & Information Structure. Discourse & Dialogue CS 359 October 11, 2001. Discussion Questions. In Hiyakumoto et al, the prevalence of H* and L+H* accents in the BNRC is used to justify the use of these tunes for rheme and theme? Is this actually justified?

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Prosody & Information Structure

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  1. Prosody & Information Structure Discourse & Dialogue CS 359 October 11, 2001

  2. Discussion Questions • In Hiyakumoto et al, the prevalence of H* and L+H* accents in the BNRC is used to justify the use of these tunes for rheme and theme? Is this actually justified? • The authors also observe that WordNet only encodes a small set of relationships. Can we just ignore the others? • Are there any systems that implement contrastive stress? If not, why not? • How do systems handle other types of “accent”? Different languages?

  3. Roadmap • Motivation • Synthetic speech • Experimental evidence • Key components • Prosody • Syntax • Contextually “appropriate” speech synthesis

  4. 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

  5. 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?

  6. 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)

  7. “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

  8. “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

  9. ToBI Examples

  10. Contrast Examples

  11. Contrast Examples

  12. Contrast Examples

  13. 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 • Lavage=H*L-L%; NP:lavage’;u:rheme

  14. 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

  15. 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)

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

  17. 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.

  18. 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

  19. 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%

  20. 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

  21. 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, ….

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