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 - , 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(a j,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 Structure A: There is an engine at Avon B: It is hooked to a boxcar. ce1 ce2 s s’ s’’ x w e ce1: 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

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