1. Discourse Analysis Natural Language Understanding basis
June 2016, Informatics– Ibrahim Dahmash
Discourse Analysis Natural Language Understanding basis

2. George: Well I imagine she was a very attractive woman.
Gracie: Oh yeah…and then Mr. and Mrs. Jones were having matrimonial trouble, and my brother hired to watch Mrs. Jones.
George: Well I imagine she was a very attractive woman.
Gracie: She was, and my brother watched her day and night for six months.
George: Well, what happened?
Gracie: She finally got divorce.
George: Mrs. Jones ?!
Gracie: No, my brother’s wife.
George Burns and Gracie Allen in The Salesgirl
Ibrahim Dahmash
Discourse Analysis

3. Motivation and Question
To achieve the coherence of (sentences, words) in the dialogue
By Discourse Analysis
How to Do a Discourse Analysis ?!
By focus on some of Cohesive Devices.
Ibrahim Dahmash
Discourse Analysis

4. Introduction
Language consists of collocated, related groups of sentences. We refer to such a group of sentences as a discourse.
The word 'discourse' comes from Latin 'discursus' which denoted 'conversation, speech'.
There are two basic forms of discourse:
Monologue.
Dialogue.
Ibrahim Dahmash
Discourse Analysis

5. Reference Resolution General Example:
John went to Bill’s car dealership to check out a Honda Civic. He looked at it for about an hour.
Reference: the process by which speakers use expressions to denote an entity.
Referring expression: expression used to perform reference .
Referent: the entity that is referred to.
Co-reference: referring expressions that are used to refer to the same entity.
Anaphora: reference to a previously introduced entity.
Cataphoric: referring forward. It refers the entity what is being expressed and what is to be expressed.
Ibrahim Dahmash
Discourse Analysis

6. Reference Resolution Discourse Model
It contains representations of the entities that have been referred to in the discourse and the relationships in which they participate.
Two components required by a system to produce and interpret referring expressions.
A method for constructing a discourse model that evolves dynamically.
A method for mapping between referring expressions and referents.
Ibrahim Dahmash
Discourse Analysis

7. Reference Resolution Five common types of referring expression Type
Example
Indefinite noun phrase
I saw a Honda Civic today.
Definite noun phrase
I saw a Honda Civic today. The Civic was white.
Pronoun
I saw a Honda Civic today. It was white.
Demonstratives
I like this better than that.
One-anaphora
I saw 6 Honda Civic today. Now I want one.
Three types of referents that complicate the reference resolution
Inferrables
I almost bought a Honda Civic, but a door had a dent and the engine seemed noisy
Discontinuous Sets
John and Mary love their Civics. They often drive them.
Generics
I saw 6 Honda Civic today. They are the coolest cars.
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Discourse Analysis

8. Reference Resolution How could a computer resolve these references?
First, The set of possible referents by certain hard-and-fast constraints.
Second, set the preferences for possible referents.
Ibrahim Dahmash
Discourse Analysis

9. Constraints Number Agreement: Gender Agreement:
To distinguish between singular and plural references.
*John has a new car. They are red.
Gender Agreement:
To distinguish male, female, and non-personal genders.
John has a new car. It is attractive. [It = the new car]
Person and Case Agreement:
To distinguish between three forms of person.
*You and I have Civics. They love them.
To distinguish between Nominative position, Accusative position, and genitive position.
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Discourse Analysis

10. Constraints Syntactic Constraints: Selectional Restrictions:
Syntactic relationships between a referring expression and a possible antecedent noun phrase
John bought himself a new car. [himself=John]
John bought him a new car. [him ≠ John]
Selectional Restrictions:
A verb places restrictions on its arguments.
John parked his Honda in the garage. He had driven it around for hours. [it=Honda, it ≠ garage]
I picked up the book and sat in a chair. It broke [it=a chair]
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Discourse Analysis

11. Preferences Recency: Grammatical Role:
Entities introduced recently are more salient than those introduced before.
John has a Legend. Bill has an Civic. Mary likes to drive it.
Grammatical Role:
Entities mentioned in subject position are more salient than those in object position.
Bill went to the Honda dealership with John. He bought an Civic. [he=Bill]
Ibrahim Dahmash
Discourse Analysis

12. Preferences in Pronoun Interpretation
Repeated Mention:
Entities that have been focused on in the prior discourse are more salient.
John needed a car to get to his new job.
He decided that he wanted something sporty.
Bill went to the Honda dealership with him.
He bought an Civic. [he=John]
Parallelism:
There are also strong preferences that appear to be induced by parallelism effects.
Mary went with Sue to the cinema. Sally went with her to the mall. [ her = Sue]
Jim surprised Paul and then Julie shocked him. [him = Paul]
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Discourse Analysis

13. Preferences in Pronoun Interpretation
Verb Semantics:
Certain verbs appear to place a semantically-oriented emphasis on one of their argument positions.
John telephoned Bill. He had lost the book in the mall. [He = John]
John criticized Bill. He had lost the book in the mall. [He = Bill]
David praised Hans because he. [he = Hans]
David apologized to Hans because he. [he = David]
Ibrahim Dahmash
Discourse Analysis

14. Preferences more difficult than constrains
how can one integrate these different preferences?
Tree Search Algorithm (Hobbs 1978)
Salience Factors Algorithm (Lappin and Leass 1994)
Centering Theory Algorithm (Grosz et al., 1995)
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Discourse Analysis

15. Devices for Discourse
Cohesion - grammatical role relationship between parts of a sentence essential for its interpretation.
Anaphoric Relation
John has three new Civics. They are red.
Cataphoric Relation
Here is the 9, O Clock news.
Coherence - the order of statements(the meaning) relates one another by sense.
John hid Bill’s car keys, he was drunk.
Parallelism - means side by side.
Mary went with Sue to the Honda dealership. Sally went with her to the Mazda dealership [her = Sue] ??
Ibrahim Dahmash
Discourse Analysis

16. Devices for Discourse
Speech Events - are mainly concerned what people say in different environment e.g. Debate, interview, discussions, quiz etc. are different Speech Events. Speakers may have different speech roles as friend, strangers, young or old of equal or unequal status.
Background Knowledge - can be very much helpful in interpreting any text. Schema and script are two terms that comprise the background knowledge. Schema and script tells us what actually the real situation is and what the actions are.
Trying not to be out of the office Suzy went into the nearest place, sat down and ordered an apple.
Schema - Suzy may be an office girl.
Script - She walked to the nearest supermarket.
Conversational Interaction - is an activity where for the most part two or more people take turn at speaking: in these turns at speaking one has to pick up the completion point to take his turn to speak. This is conversational interaction.
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Discourse Analysis

17. Monologue Versus Dialogue
One difference between monologue and dialogue is that dialogue is characterized by turn-taking, grounding and implicature. Implicature like ‘Some dogs are mammals’ , the speaker conveys by implicature that not all dogs are mammals. Finally, Both of them exhibit anaphora and discourse structure and coherence.
Implicature like ‘Some dogs are mammals’ , the speaker conveys by implicature that not all dogs are mammals.
Finally, Both of them exhibit anaphora and discourse structure and coherence.
Ibrahim Dahmash
Discourse Analysis

18. References
Speech and Language Processing "Jurafsky and Martin (2009), chapter 18, 19, 21“
Speech Language understanding systems for extracting semantic information from speech  "Tur and Demori (2011), chapter 3, 10, 11"
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Discourse Analysis

19. Further Reading
Speech Language understanding systems for extracting semantic information from speech  "Tur and Demori (2011), chapter 3, 10, 11, 15“.
An Introduction to Critical Discourse Analysis in Education Second Edition by Rebecca Rogers.
DISCOURSE ANALYSIS, GILLIAN BROWN and GEORGE YULE.
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Discourse Analysis

20. Thanks for your attention
Ibrahim Dahmash
Discourse Analysis

21. Questions