Intention & Cooperation

Discourse and Dialogue

CS 359

October 18, 2001

Questions

• Do systems do conversational implicature?

• What sorts of knowledge representations are used in dialogue systems?

• Are there systems that incorporate planning, dialogue act recognition?

• Has anyone tried applying these techniques to other conversational styles - e-mail, IM?

• 60-80% accurate subsystems, how bad is the whole thing?

Dialogue Management:Reading & Reporting

• Dialogue Management overview

– Spoken Dialogue Technology, McTear

• State based systems

– Design issues (McTear)

– Automatic learning (Woszczyna & Waibel)

• Frame-based systems: SunDIAL (Peckhem at al)

• Plan based systems

– Theorem proving (Smith et al)

– TRAINS (BDI): Allen et al

– Rational Agency “Artimis” - Sato & de Mori

Roadmap

• Structure of Discourse (G&S 1986)– Attention to Intention

• Planning and Cooperation– Cooperative meaning: Grice’s Maxims– Cooperative action:

• STRIPS planning basics

• Shared plans

• Discourse and Domain plans

Discourse Structure

• Attentional Structure:– Focus– Reference– Information Structure: Given/New

• Intentional Structure:– Discourse purpose (DP)

• Discourse segment purpose (DSP)• Contribute to overall goal of conversation

• Linguistic structure organizes/executes

Cooperation in Communication

• Conversational participants act together– Speakers must provide sufficient information

about beliefs and intentions for hearers to interpret as part of plan

– Hearers must recognize cues in language and structure of discourse to constrain inference of plan

Cooperative Meaning

• Cooperative Principle: Grice 1975– Make conversational contribution as required at

stage of discourse by accepted discourse goal

• Maxims:– Quantity – Quality– Relation– Manner

Maxim of Quantity

• Be as informative as necessary– Be no more informative than necessary

• E.g.”I saw three ducks”->– “I saw EXACTLY three ducks”

Maxim of Quality

• Do not say that which you believe to be false– Don’t say things without evidence

• E.g. “I saw ducks” implicates that you really did

Maxim of Relation

• Be relevant– Utterances should relate to each other and

overall discourse goals– Focus, coherence, reference all rely on relation

• E.g. A:I am out of gas.

• B:There’s a garage around the corner.

Maxim of Manner

• “Be perspicuous”– Avoid ambiguity– Avoid obscurity– Be brief– Be orderly

Maxims and Meaning

• In cooperative discourse, expect maxims will be followed.

• However,– Violate or “opt out”– One or another may be violated in case of clash– Flout: Deliberately, blatantly break

• “Exploit” maxim to create conversational implicature– Meaning outside of literal sense

• E.g. irony, metaphor, hyperbole, etc...

Planning & Plan Recognition

• Discourse planning based on classic AI– STRIPS (Nilson et al)

• Plan: Sequence of actions from start to goal• Action model: “Operator”

– “IF”: precondition for action– “ADD”,”DELETE”: effect on state of action– “BODY”: subactions

• Recognition: Links beliefs & desires to preconditions and goals

Plan Example

Planning Issues

• Complexity– Forward-chaining: simple, but exponential– Backward-chaining: Can reduce search

• Assumes single actor, single plan– Full control- ‘master-slave’

• Need notions of generation, enablement, simultaneous action, maintenance

Shared Plans

• Tie belief and intention to plans (Pollack 86)– Beliefs about: relations among actions

(enablement, generation) and executability– Intentions (of agent) about actions

• Multiple collaborative agents• Not just simultaneous private plans• Belief => Mutual belief• Different agents, different actions

Collaborative Plans

Plan => Shared Plan

• SimplePlan(G,an,[a1..an-1],t1,t2)• BEL(G,EXEC(ai,G,t2),t1)

• & BEL(G,GEN(ai,ai+1,G,t2),t1) • & INT(G,ai,t2,t1)• & INT(G,BY(ai,ai+1),t2,t1)

• BEL: Believe• INT: Intend• EXEC: Execute• GEN: Generate• BY: By

• SharedPlan(G1,G2,A)• MB(G1,G2,EXEC(aj,Gaj)

• MB(…)

• MB(G1,G2,INT(Gaj,aj))

• MB(G1,G2,INT(Gaj,BY(aj,A))

• INT(Gaj,aj)

• INT(Gaj,BY(aj,A))

Cooperative Plan Maxims

• Conversational Default Rule1 (CDR1)

• MB(G1,G2,Desire(G1,P) &– Cooerative(G1,G2,P) &– Communicating (G1,G2,Desire(G1,P)

• MB(G1,G2,Desire(G1,

• Achieve(SharedPlan(G1,G2,Achieve(P))))

•

Cooperative Plan Maxims

• Conversational Default Rule 2 (CDR2)• SharedPlan* = Partial Shared Plan• [SharedPlan*(G1,G2,Achieve(P)) &• MB(Desire(G1,Do(G2,Action)) &• MB(G1,G2,Exec(G2,Action) &• MB(G1,G2,Contribute(Action,Achieve(P)))]• Intend(G2,Action) &• MB(G1,G2,Intend(G1,G2,Intend(G2,Action)|)

Action Schemas

• Simultaneous action

• Conjoined actions

• Sequential actions

• Single Actor plans

Shared Plan Summary

• Intentional structure– Intentions

• Relations: Dominance, Satisfaction-precedence

– Discourse segments correspond to intentions

• Plans in collaborative, task-oriented discourse– Not fixed, negotiated– Intended to be recognized– Propose plan; accept/deny; refine beliefs,

intentions,plans,.,

Limitations of Shared Plans

• Only handles domain planning– No treatment of discourse plans

• Turn-taking, clarification, openings…

• Only addresses intentional structure– Doesn’t integrate attentional structure

• Information flow, focus, reference

Proposal: Unified Framework

• Integrate disparate components of discourse theory– Semantics: accessible referents– Attentional state– Intentional structure

• Common structures form”threads”,”scripts”

– Speech acts - functional, informational– Dialogue acts

DRT-Style Combined StructureA: There is an engine at AvonB: It is hooked to a boxcar.

ce1 ce2 s s’ s’’

x w ece1: asrt(A,B,engine(x) (s) (s’))

Avon(w)e:at(x,w)y u e’

ce2: asrt(B,A, boxcar(y) (s’) (s’’))e’:hook(y,u)

u is x

Conversation Acts

Discourse Level Act Type Sample Acts

Sub-utterance Turn-taking Take-turn, keep-turn, assign-turn

Utterance Unit Grounding(Acknowledge)

Initiate, continue,ack, repair, cancel

Discourse Unit Core Speech Acts Inform,ynq,check,eval, accept

MultipleDuscourse Units

Argumentation Elaborate, clarify,Convince, q&a

Mental States & Dialogue Acts

• Incorporate mental states in “s” of structure– Encode belief, attention, obligation..– Belief = MB– Situation S’ inherits all of S

• Dialogue Acts– Statement (assert), Open-option, Offer, Commit– Acts bring about effects

• Me; ntal states, event types

• E.g. Commit -> Obliged

Threads

• Intentional organization:– Events grouped into “threads”

• Threads “dominate” events

• Events are ordered

• Identify specific thread types– Argumentation acts= rhetorical relations: RST

• Elaboration, etc

– Predictable: activities - “scripts”,• Known conversational styles

• Provide expectations, predict subsequent moves

Summary

• Discourse as collaboration– Gricean conversational maxims

• Cooperative principle

– Cooperative task-oriented plans• “SharedPlan’

• Use mutual belief, negotiation of plan, act timing

• Integrated discourse model– Combine semantics, attentional, intentional state,

conversational act strategy

Challenges

• Conversational act recognition– “Okay’

• Domain plan recognition– Collection

Conversation Acts

Extend speech acts for conversational control