1. Discourse & Dialogue CMSC 35900-1 October 28, 2004
What’s New?
Discourse & Dialogue
CMSC
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 Now, generation and synthesis
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 Unstressed -> Given, salient
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 “Default” sentence intonation
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
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 X 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%