Dialogue Structure and Plan/Agent-based Dialogue … · 2 FS2 Restaurant DSP 1 FS1 Suburb 3 FS3 ......

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Dialogue Structure andPlan/Agent-basedDialogue Models

Slides adapted from Arne JönssonLinköping University, Linköping, Sweden

Topics in Human Computer Interaction

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Dialogue and DiscourseStructure

Topics in Human Computer Interaction

LN3 Topics in HCI, Summer Semester 2015 3

Discourse Structure (Grosz & Sidner, 1986)Three components • Linguistic structure• Intentional structure• Attentional state

LN3 Topics in HCI, Summer Semester 2015 4

Linguistic Structure• Discourse segments and relationships that can

hold between them• Discourse segment – a sequence of utterances• Indicators of segment boundaries:

– Cue phrases– Intonation– Changes in tense and aspect

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Cue Phrases – Examples• By the way• For example,• Bye• Oops, I forgot• First of all, finally• OK• But• Thus

• digression• start elaboration• end dialogue• flashback• enumeration• end topic• introduce subtopic• conclusion

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Intentional Structure• A discourse has an overall discourse purpose

(DP)• The discourse purpose gives:

– The reason a linguistic act was performed – The reason the particular content was conveyed

• Every discourse segment has its own discourse segment purpose (DSP)

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Intentions• The intentions must be recognized from

DSP or DP• Intend that some agent:

– intend to perform some physical task– believe some fact– believe that one fact supports another– intend to identify an object– know some property of an object

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Structural Relations• Dominance (DOM)

– DSP1 DOM DSP2 ifDSP2 contributes to DSP1

• Satisfaction-precedence (SP)– DSP1 SP DSP2 if

DSP1 must be satisfied before DSP2

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Attentional State• Abstraction of the participants’ focus of attention

– A property of the discourse, not the participants• Dynamic – records objects, properties and

relations that are salient at each point in the discourse

• Modeled by a set of focus spaces in a stack• Focusing structure – the collection of focus

spaces available at any time• Focusing process – the process of manipulating

focus spaces

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Focus Stack – ExampleU: Where can I find a good restaurant?

Type of foodDSP2 FS2

RestaurantDSP1 FS1

SuburbDSP3 FS3

S: What type of food do you want?

U: Thai.S: Ok. Any specific suburb?

DSP1 DOM DSP2DSP1 DOM DSP3

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Complex Dialogue Models

Topics in Human Computer Interaction

LN3 Topics in HCI, Summer Semester 2015 12

Dialogue Management ApproachesDialogue Grammars

Plan-based and Belief Desire Intention (BDI) models

Statistical Models

Formalism Grammars Plans Conditional probabilities

Processing method

Parser Plan recognition StatisticalInference

Performance + Efficient + Powerful + Efficient

Restrictive Not so efficient Can go wrong

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Complex Dialogue Modeling Paradigms• Plan (Task) Based Model: The dialogue

involves interactively constructing a plan• Agent-Based Model: Involves planning and

also executing and monitoring operations in a dynamically changing world

• Statistical Model: Learns the system’s behaviour

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Planning

Topics in Human Computer Interaction

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Planning• Given a goal state

– find a sequence of actions to reach the goal state– specify the bindings of the parameters for the actions

• Plan generation assumes– a world model– an action model– a problem-solving strategy

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Key Ideas behind Planning• Use a formal language to describe states,

actions and goals– States and goals are represented by clauses, and

actions by logical descriptions of preconditions and effects

• The planner can add actions to a plan wherever they are needed

• Most parts of the world are independent of other parts

– Divide and conquer approach– But need to detect interactions between sub-parts

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ActionsAn action (plan operator) A is defined by• preconditions

– what has to be true in order for someone to do A• body

– how A can be divided into sub-actions• effects

– what is true after A is done> intended effects – the goal of A > side-effects

• constraints on entities involved in A

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Planning an Action – Regression PlannerGiven a goal G• Find all operators such that G is on their effect list• Choose an operator O• For each precondition P of O

– If P does not hold, post P as a subgoal to be achieved before doing O

Distinction between preconditions and constraints• Need to check constraints and eliminate operators

whose constraints are not satisfied

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Planning Example – Making Coffee (I)

• Initial state – have water, have grinder, be at kitchen, store exists, kitchen exists

• Goal state – have a cup of coffee

• Operators

Operator Precondition Effect

PourCoffee Have brewed coffee

Have cup of coffee

MakeCoffee Have beansHave grinderHave boiling waterBe at kitchen

Have brewed coffee

Buy y Be at storeHave money

Have y

GoPlace x Place x exists Be at xGetMoney Be at bank Have moneyBoilWater Be at kitchen

Have waterHave boiling water

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Buy brewed coffee Make coffee

Have beans Have grinder

Pour coffee

Have brewed coffee

Planning Example – Making Coffee (II)

Have cup of coffee

Buy beans

Have money At store

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Plan-based Dialogue Models

Topics in Human Computer Interaction

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Plan-based Dialogue ManagementKey idea: “language as action”• Need to recognize intent of an utterance• The task to be performed has subgoals or

preconditions – Actions performed to satisfy them include dialogue acts

• Effects of dialogue acts include changing the belief state of the hearer

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Planning and Recognizing Dialogue ActsUtterance generation as planning• Given a communicative goal G and a set of

dialogue act plan operators, generate a plan to achieve G

Dialogue act recognition as plan recognition• Given an utterance U by speaker S, find a

communicative goal G and a plan P to achieve G such that U is a part of P, and S might plausibly have the goal G

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Plan-based Theory of Speech Acts (Cohen & Perrault, 1979)

• Based on beliefs, wants, and the interaction between them

• Beliefs – should represent that AGT1 believes that AGT2 believes whether proposition P is true, without AGT1 having to know whether P or ~P is true

– Basic operator: BELIEVE(A,P)– Nesting: BELIEVE(AGT1,BELIEVE(AGT2,P))

• Goals –– WANT(AGT1,BELIEVE(AGT2,P))– BELIEVE(AGT1,WANT(AGT2,P))

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Models of Plans• Operators – transform the planner’s model of

the world• Form of operators:

– Effects – propositions to be added to the model of the world

– Preconditions –> can.pr – must be true in the world model for the

operator to be applicable> want.pr – the agent must want to do the action

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• INFORM(S,H,P)want.precond: BELIEVE(S,WANT(S,INFORM(S,H,P)))can.precond: BELIEVE(S,P)effect: BELIEVE(H,BELIEVE(S,P))

• CONVINCE(S,H,P)can.precond: BELIEVE(H,BELIEVE(S,P))effect: BELIEVE(H,P)

SPEAKER

Sample Speech Acts as Plan OperatorsHEARER

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Example: A Plan to InformS BELIEVE S WANT:

BELIEVE(H,P)

CONVINCE(S,H,P)effect

INFORM(S,H,P)effect

BELIEVE(S,P)can.precond

BELIEVE(H,BELIEVE(S,P))can.precond

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Allen and Perrault (1980)• Incorporated knowledge about beliefs• Applied to

– discourse interpretation (recognizing intentions from utterances)

– response generation (related to discourse planning)

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Knowledge about Belief• Three types of knowledge about belief

– S believes that A knows that P is trueBELIEVE(S,(P & BELIEVE(A,P))), i.e.,BELIEVE(S, A KNOW P), where

A KNOW P = P & BELIEVE(A,P)– A knows whether P is true

A KNOWIF P = (P & BELIEVE(A,P)) ν (~P & BELIEVE(A,~P))

– A knows the value of a description ix:D(x)A KNOWREF D =

)),(:i BELIEVE(A, &)),(:i( yxDxyxDxy

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Additional Speech Acts (I)• INFORM(S,H,P)

want.precond: WANT(S, INFORM(S,H,P))can.precond: S KNOW Peffect: H KNOW PE.g., “HCI is offered at 4 pm”

INFORM(S,H,Offered(HCI,4pm))

• REQUEST(S,H,action)effect: WANT(H, DO(H,action))E.g., “Get me a coffee’’

REQUEST(S,H, Get(H,S,coffee))

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Additional Speech Acts (II)• INFORMIF(S,H,P) – inform if P is true or false

want.precond: WANT(S, INFORMIF(S,H,P))can.precond: S KNOWIF Peffect: H KNOWIF PE.g., “Is HCI offered at 3 pm?”

REQUEST(S,H,INFORMIF(H,S,Offered(HCI,3pm))• INFORMREF(S,H,description(P)) – inform a value that

makes P truewant.precond: WANT(S, INFORMREF(S,H,description(P)))can.precond: S KNOWREF description(P)effect: H KNOWREF description(P)E.g., “When is HCI offered?”

REQUEST(S,H,INFORMREF(H,S, time t such thatOffered(HCI,t))

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Notation: SBAW(X) –i/c SBAW(Y)• Rules concerning actions• Rules concerning knowledge• Rules concerning planning by others

Plan Inference Rules

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Rules Concerning Actions• Precondition-Action Rule

SBAW(P) –i SBAW(ACT)if P is a precondition of action ACT

• Body-Action RuleSBAW(B) –i SBAW(ACT)if B is part of the body of action ACT

• Action-Effect RuleSBAW(ACT) –i SBAW(E)if E is an effect of action ACT

• Want-Action RuleSBAW(nW(ACT)) –i SBAW(ACT)if n is the agent of action ACT

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Rules Concerning Knowledge• Know-positive Rule

SBAW(A KNOWIF P) –i SBAW(P)

• Know-negative RuleSBAW(A KNOWIF P) –i SBAW(~P)

• Know-value RuleSBAW(A KNOWIF P(a)) –i SBAW(A KNOWREF ix:P(x))

• Know-term RuleSBAW(A KNOWREF ix:D(x)) –i SBAW(P(ix:D(x)))

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Rules Concerning Planning by Others• Action-Precondition Rule

XW(ACT) –c XW(P)if P is a precondition of action ACT

• Action-Body RuleXW(ACT) –c XW(B)if B is part of the body of action ACT

• Effect-Action RuleXW(E) –c XW(ACT)if E is an effect of action ACT

• Know RuleXW(P) –c XW(X KNOWIF P)

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Controlling Plan Inference• Main elements

– Expectations – possible goals in the domain– Alternatives – plans emerging from the observations

• Plan specification– Infer – suggest inference rules that apply– Expand – apply rules to modify the plan

• Accept a plan – an alternative meets an expectation

– Heuristics are applied to rate a plan

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Example – The BOARD Plan

SBAW(WANT(S,Informref(S,A,i(x:time): DEPART.TIME(train1,x)))) Want-action

SBAW(Informref(S,A,i(x:time): DEPART.TIME(train1,x))) effect (Speech Act)

SBAW(A KNOWREF i(x:time): DEPART.TIME(train1,x))

Know-termSBAW(P?(i(x:time): DEPART.TIME(train1,x)))

match with expectationAT(…,ix:DEPART.TIME(train1,x))

BOARD(A,train1,Toronto)|

AT(A,il:DEPART.LOC(train1,l),it:DEPART.TIME(train1,t))

INFER-EXPAND

INFER-EXPAND

ACCEPT

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Composite DAs as Plan OperatorsConvinceByInform(Speaker, Hearer, Prop)

Constraints: Agent(Speaker), Agent(Hearer), Proposition(Prop), Bel(Speaker, Prop)

Preconditions: At(Speaker, Loc(Hearer))Effects: Bel(Hearer, Prop)

MotivateByRequest(Speaker, Hearer, Act)Constraints: Agent(Speaker), Agent(Hearer), Action(Act)Preconditions: At(Speaker, Loc(Hearer))Effects: Intend(Hearer, Act)

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Trains – Example I (Allen et al., 1995) U: There's been an ice storm off Lake Ontario. Rochester and

Sodus are without power. We need to get emergency crews there as soon as possible.

C: <fig> There are power crews available at Jamestown and Ithaca. And reserve crews without trucks at Dansville. How many do you need?

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Trains – Example II (Allen et al., 1994) U: There's been an ice storm off Lake Ontario. Rochester and

Sodus are without power. We need to get emergency crews there as soon as possible.

C: <fig> There are power crews available at Jamestown and Ithaca. And reserve crews without trucks at Dansville. How many do you need?

U: Well, all of them. C: OK. You'll need extra equipment then, which is at the depot

in Bath. U: OK, can you schedule the transport? C: No, The storm's affected Mount Morris as well. It's unlikely

we can get trains through there. OK. We can route it through Sodus instead.

U: No. Go via Avon. I want to get crews to Rochester as soon as possible.

C: OK

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Trains – Domain Plan Example

Repair_power(X)¬Power(X) Power(X)

Power_Crew(P) Equipment(E)At(X,P)

Transport(E,X,Y)

Precond Effect

Precond

Effect

Precond

At(Y,E) Clear_road(R,Y,X)

Effect

Precond

Transport(P,Y,X)

At(Y,P)Clear_road(R,Y,X)

Precond

At(X,E)ConstraintsConstraints

ConstraintsConstraints

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Trains – Example IIIU: No. Go via Avon. I want to get crews to

Rochester as soon as possible.

MotivateByRequest(U, C,Transport(Crews, Avon, Rochester))

Constraints: Agent(U), Agent(C), Action(Transport) Preconditions: At(U, Loc(C))Effects: Intend(C, Transport(Crews, Avon, Rochester))

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Plan-based Dialogue Management • Advantages

– Tight integration between task performance and dialogue interaction

– Complex dialogue strategies can be implemented as generic operations

– Task-dependent dialogue strategies can be added• Disadvantage

– Large knowledge engineering effort

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Agent-basedDialogue Models

Topics in Human Computer Interaction

LN3 Topics in HCI, Summer Semester 2015 46

The BDI Model – A Plan-based ModelThree components:• Beliefs about the world – how things are

perceived by an agent• Desires – how an agent wants things to be

(goals)• Intentions – an agent’s commitment to its

desires (goals) and to the plans selected to achieve these goals

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Example – BDI Dialogue Agents

Multi-agent conversation in the marketplace

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Reading Material• Towards conversational human-computer interaction, Allen

et al. (2001)• Attention, Intentions and the structure of discourse, Grosz

and Sidner (1986)• Elements of a Plan-Based Theory of Speech Acts, Cohen

and Perrault (1979)• Analyzing intention in utterances, Allen and Perrault (1980)• The TRAINS Project: A case study in building a

conversational planning agent, Allen et al. (1995)• Can I finish? Learning when to respond to incremental

interpretation results in interactive dialogue, DeVault, Sagae and Traum (2009)

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