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Argumentation in Agent Systems Part 2: Dialogue . Henry Prakken EASSS-07 31-08-2007. Why study argumentation in agent technology?. For internal reasoning of single agents Reasoning about beliefs, goals, intentions etc often is defeasible For interaction between multiple agents

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Argumentation in agent systems part 2 dialogue

Argumentation in Agent SystemsPart 2:Dialogue

Henry Prakken

EASSS-07

31-08-2007


Why study argumentation in agent technology
Why study argumentation in agent technology?

  • For internal reasoning of single agents

    • Reasoning about beliefs, goals, intentions etc often is defeasible

  • For interaction between multiple agents

    • Information exchange involves explanation

    • Collaboration and negotiation involve conflict of opinion and persuasion


Overview
Overview

  • Recent trends in argumentation logics

    • Argument schemes

    • Epistemic vs. practical reasoning

  • Argumentation in dialogue

    • Dialogue game approach

    • Types of dialogues

      • How they involve argumentation

    • The notion of commitment

  • Some dialogue systems

  • Agent behaviour in dialogues

  • Research issues


Argument schemes general form
Argument schemes: general form

  • The same as logical inference rules

  • But also critical questions

    • Pointers to undercutters

Premise 1, … , Premise n

Therefore (presumably), conclusion


Statistical syllogism
Statistical syllogism

  • P and if P then usually Q is a reason to believe that Q

    • Birds usually fly

  • Critical question: subproperty defeater?

    • Conflicting generalisation about an exceptional class

      • Penguins don’t fly


  • Normative syllogism
    “Normative syllogism”

    • P and if P then as a rule Q is a reason to accept that Q

    • Critical question: are thereexceptions?

      • How does a lawyer argue for exceptions to a rule?

        • Say legislation makes an exception

        • Say it is motivated by the rule’s purpose

        • Find an overruling principle

        • Argue that rule application has bad consequences


    Witness testimony
    Witness testimony

    • Critical questions:

      • Is W sincere? (veracity)

      • Did W really see P? (objectivity)

      • Did P occur? (observational sensitivity)

    Witness W says P

    Therefore (presumably), P


    Temporal persistence
    Temporal persistence

    • Critical questions:

      • Was P known to be false between T1 and T2?

      • Is the gap between T1 and T2 too long?

    P is true at T1 and T2 > T1

    Therefore (presumably), P is

    Still true at T2


    Arguments from consequences
    Arguments from consequences

    • Critical questions:

      • Does A also have bad consequences?

      • Are there other ways to bring about the good consequences?

    Action A brings about good consequences

    Therefore (presumably), A should be done


    Types of dialogues walton krabbe

    Dialogue Type

    Dialogue Goal

    Initial situation

    Persuasion

    resolution of conflict

    conflict of opinion

    Negotiation

    making a deal

    conflict of interest

    Deliberation

    reaching a decision

    need for action

    Information seeking

    exchange of information

    personal ignorance

    Inquiry

    growth of knowledge

    general ignorance

    Types of dialogues (Walton & Krabbe)


    Example

    P: I offer you this Peugeot for $10000.

    P: why do you reject my offer?

    P: why are French cars no good?

    P: why are French cars unsafe?

    P: Meinwagen is biased since German car magazines usually are biased against French cars

    P: why does Meinwagen have a very high reputation?.

    P: OK, I accept your offer.

    O: I reject your offer

    O: since French cars are no good

    O: since French cars are unsafe

    O: since magazine Meinwagen says so

    O: I concede that German car magazines usually are biased against French cars, butMeinwagen is not since it has a very high reputation.

    O: OK, I retract that French cars are no good. Still I cannot pay $10.000; I offer $8.000.

    Example


    Example 2

    P: I offer you this Peugeot for $10000.

    P: why do you reject my offer?

    P: why are French cars no good?

    P: why are French cars unsafe?

    P: Meinwagen is biased since German car magazines usually are biased against French cars

    P: why does Meinwagen have a very high reputation?.

    P: OK, I accept your offer.

    O: I reject your offer

    O: since French cars are no good

    O: since French cars are unsafe

    O: since magazine Meinwagen says so

    O: I concede that German car magazines usually are biased against French cars, but Meinwagen is not since it has a very high reputation.

    O: OK, I retract that French cars are no good. Still I cannot pay $10.000; I offer $8.000.

    Example (2)


    Example 3

    P: I offer you this Peugeot for $10000.

    P: why do you reject my offer?

    P: why are French cars no good?

    P: why are French cars unsafe?

    P: Meinwagen is biased since German car magazines usually are biased against French cars

    P: why does Meinwagen have a very high reputation?.

    P: OK, I accept your offer.

    O: I reject your offer

    O: since French cars are no good

    O: since French cars are unsafe

    O: since magazine Meinwagen says so

    O: I concede that German car magazines usually are biased against French cars, but Meinwagen is not since it has a very high reputation.

    O: OK, I retract that French cars are no good. Still I cannot pay $10.000; I offer $8.000.

    Example (3)


    Dialogue systems according to carlson 1983
    Dialogue systems (according to Carlson 1983)

    • Dialogue systems define the conditions under which an utterance is appropriate

    • An utterance is appropriate if it furthers the goal of the dialogue in which it is made

    • Appropriateness defined not at speech act level but at dialogue level

    • Dialogue game approach


    Dialogue game systems
    Dialogue game systems

    • A dialogue purpose

    • Participants (with roles)

    • A communication language Lc

      • With embedded topic language Lt and a logic for Lt

    • A protocol for Lc

    • Effect rules for Lc (“commitment rules”)

    • Termination and outcome rules


    Some history
    Some history

    • In philosophy: formal dialectics

      • (Hamblin 1970, MacKenzie 1979, Walton & Krabbe 1995, …)

      • Deductive setting

    • In AI: procedural defeasibility

      • Loui (1998(1992)), Brewka (1994,2001)

      • Adding counterarguments

    • In AI & Law: dispute resolution

      • (Gordon 1993, Bench-Capon 1998, Lodder 1999, Prakken 2000-2006, …)

      • Adding counterarguments and third parties

    • In MAS: agent interaction

      • Parsons-Sierra-Jennings 1998, Amgoud-Maudet-Parsons 2000, McBurney-Parsons 2002, …

      • Adding agents


    Persuasion
    Persuasion

    • Participants:proponent (P) and opponent (O) of a dialogue topic t

    • Dialogue goal:resolve the conflict of opinion on t.

    • Participants’ goals:

      • P wants O to accept t

      • O wants P to give up t

    • Typical speech acts:

      • Claim p, Concede p, retract p, Why p, p since S, …


    Information seeking
    Information seeking

    • Dialogue goal: information exchange

    • Agent’s goals: learning(?)

    • Typical speech acts:

      • Ask p, Tell p, Notell p, …


    Negotiation
    Negotiation

    • Dialogue goal: agreement on reallocation of scarce resources

    • Participants’ goals: maximise individual gain

    • Typical communication language:

      • Request p, Offer p, Accept p, Reject p, …


    Deliberation
    Deliberation

    • Participants:any

    • Dialogue goal:resolve need for action

    • Participants’ goals:

      • None initially

    • Possible set of speech acts:

      • Propose, ask-justify, prefer, accept, reject, …


    Dialectical shifts to persuasion
    Dialectical shifts to persuasion

    • Information exchange: explaining why something is the case or how I know it

      • Persuasion over fact

    • Negotiation: explaining why offer is good for you or bad for me

      • Persuasion over fact or action

    • Deliberation: explaining why proposal is good or bad for us

      • Persuasion over fact or action


    Commitment in dialogue
    Commitment in dialogue

    • Walton & Krabbe (1995):

      • General case: commitment to action

      • Special cases:

        • Commitment to action in dialogue (dialogical or propositional commitment)

        • Commitment to action outside dialogue (social commitment)

      • Negotiation and deliberation lead to social commitments

      • Persuasion leads to dialogical commitments


    Quality aspects of dialogue protocols
    Quality aspects of dialogue protocols

    • Effectiveness: does the protocol further the dialogue goal?

      • Commitments

      • Agents’ logical and dialogical consistency

      • Efficiency (relevance, termination, ...)

    • Fairness: does the protocol respect the participants’ goals?

      • Flexibility, opportunity, …

    • Public semantics: can protocol compliance be externally observed?


    Effectiveness vs fairness
    Effectiveness vs fairness

    • Relevance and efficiency: moves should be related to the dialogue topic

      • Relevance often enforced in rigid so efficient “unique-move immediate response” protocols

      • But sometimes participants must have freedom to backtrack, to explore alternatives, to postpone responses, …


    Public semantics commitments in persuasion
    Public semantics:Commitments in persuasion

    • A participant’s publicly declared standpoints, so not the same as beliefs!

    • Only commitments and dialogical behaviour should count for move legality:

      • “Claim p is allowed only if you believe p”

        vs.

      • “Claim p is allowed only if you are not committed to p and have not challenged p”


    Assertion acceptance attitudes
    Assertion/Acceptance attitudes

    • Relative to speaker’s own knowledge!

      • Confident/Thoughtful agent: can assert/accept P iff he can construct an argument for P

      • Careful/cautious agent: can assert/accept P iff he can construct an argument for P and no stronger counterargument

      • Thoughtful/skeptical agent: can assert/accept P iff he can construct a justified argument for P

    • If part of protocol, then protocol has no public semantics!


    Two systems for persuasion dialogue
    Two systems for persuasion dialogue

    • Parsons, Wooldridge & Amgoud

      • Journal of Logic and Computation 13(2003)

    • Prakken

      • Journal of Logic and Computation 15(2005)


    Pwa languages logic agents
    PWA: languages, logic, agents

    • Lc: Claim p, Why p, Concede p, Claim S, Question p

      • p  Lt, S  Lt

    • Lt: propositional

    • Logic: argumentation logic

      • Arguments: (S, p) such that

        • S  Lt, consistent

        • S propositionally implies p

      • Attack: (S, p) attacks (S’, p’) iff

        • p  S’ and

        • level(S) ≤ level(S’)

      • Semantics: grounded

    • Assumptions on agents:

      • Have a knowledge base KB  Lt

      • Have an assertion and acceptance attitude


    Pwa protocol
    PWA: protocol

    • W claims p;

    • B concedes if allowed, if not claims p if allowed or else challenges p

    • If B claims p, then goto 2 with players’ roles reversed and p in place of p;

    • If B has challenged, then:

      • W claims S, an argument for p;

      • Goto 2 for each s  S in turn.

    • B concedes if allowed, or the dialogue terminates.

    • Outcome: do players agree at termination?


    Example persuasion dialogue

    P1: My car is safe. claim

    P2: Since it has an airbag. argument

    P3: why does that not make my car safe? challenge

    P4: Yes, that is what the newspapers say, concession but that does not prove anything, since newspapers are unreliable sources of technological information undercutter

    P5: OK, I was wrong that my car is safe. retraction

    O1: Why is your car safe? challenge

    O2: That is true, concession but your car is still not safe counterclaim

    O3: Since the newspapers recently reported on airbags exploding without cause rebuttal

    O4: Still your car is not safe, since its maximum speed is very high. alternative rebuttal


    Pwa example dialogue
    PWA: example dialogue

    P: careful/cautious

    P1: claim safe

    P2: claim {airbag, airbag  safe}

    P3: claim {airbag  safe}

    O: thoughtful/cautious

    O1: why safe

    O2a: concede airbag

    O2b: why airbag  safe

    P: careful/cautious

    P1: claim safe.

    P2: whysafe

    P3a: concede newspaper

    P3b: why newspaper   safe

    O: confident/cautious

    O1: claimsafe

    O2: claim {newspaper,

    newspaper   safe}

    O3: claim {newspaper   safe}


    Pwa characteristics
    PWA: characteristics

    • Protocol

      • multi-move

      • (almost) unique-reply

      • Deterministic in Lc

    • Dialogues

      • Short (no stepwise construction of arguments, no alternative replies)

      • Only one side develops arguments

    • Logic

      • used for single agent: check attitudes and construct argument


    Prakken languages logic agents
    Prakken: languages, logic, agents

    • Lc: Any, provided it has a reply structure (attacks + surrenders)

    • Lt: any

    • Logic: argumentation logic

      • Arguments: trees of conclusive and/or defeasible inferences

      • Attack: depends on chosen logic

      • Semantics: grounded

    • Assumptions on agents: none.


    Prakken example lc with reply structure

    Acts

    Attacked by

    Surrendered by

    claim p

    why p

    concede p

    why p

    p since S

    retract p

    concede p

    retract p

    p since S

    p’ since S’

    why s (s  S)

    concede (p since S)

    concede s (s  S)

    Prakken: example Lc (with reply structure)


    Protocol variations
    Protocol variations

    • Unique-vs multiple moves per turn

    • Unique vs. multiple replies

    • Immediate response or not


    Prakken protocols basic rules
    Prakken: protocols (basic rules)

    • Each noninitial move replies to some previous move of hearer

    • Replying moves must be defined in Lc as a reply to their target

    • Argue moves must respect underlying argumentation logic

    • Termination: if player to move has no legal moves

    • Outcome: what is dialogical status of initial move at termination?


    Dialogical status of moves
    Dialogical status of moves

    • Each move in a dialogue is in or out:

      • A surrender is out,

      • An attacker is:

        • in iff surrendered, else:

        • in iff all its attacking children are out


    P1+

    O1-

    P2-

    P4+

    O2-

    O3+

    P3+


    Functions of dialogical status
    Functions of dialogical status

    • Can determine winning

      • Plaintiff wins iff at termination the initial claim is in; defendant wins otherwise

    • Can determine turntaking

      • Turn shifts if dialogical status of initial move has changed

        • Immediate response protocols (Loui 1998)

    • Can be used in defining relevance


    Relevant protocols
    Relevant protocols

    • A move must reply to a relevant target

    • A target is relevant if changing its status changes the status of the initial claim

    • Turn shifts if dialogical status of initial move has changed

      • Immediate response protocols


    P1+

    O1-

    P2-

    P4+

    O2-

    O3+

    P3+


    P1+

    O1-

    P2-

    P4+

    O2+

    O3+

    P3-

    O4+


    P1+

    O1-

    P2-

    P4+

    O2-

    O3+

    P3+


    P1-

    O1+

    P2-

    P4-

    O2-

    O3+

    O4+

    P3+



    Prakken example dialogue1
    Prakken: example dialogue

    P1: claim safe

    O1: why safe


    Prakken example dialogue2
    Prakken: example dialogue

    P1: claim safe

    O1: why safe

    P2: safe since airbag,

    airbag  safe


    Prakken example dialogue3
    Prakken: example dialogue

    P1: claim safe

    O1: why safe

    P2: safe since airbag,

    airbag  safe

    O2a: concede airbag


    Prakken example dialogue4
    Prakken: example dialogue

    P1: claim safe

    O1: why safe

    P2: safe since airbag,

    airbag  safe

    O2b: safe since newspaper,

    newspaper  safe

    O2a: concede airbag


    Prakken example dialogue5
    Prakken: example dialogue

    P1: claim safe

    O1: why safe

    P2: safe since airbag,

    airbag  safe

    O2b: safe since newspaper,

    newspaper  safe

    O2a: concede airbag

    P3a: concede newspaper


    Prakken example dialogue6
    Prakken: example dialogue

    P1: claim safe

    O1: why safe

    P2: safe since airbag,

    airbag  safe

    O2b: safe since newspaper,

    newspaper  safe

    O2a: concede airbag

    P3b: so whatsince unreliable,

    unreliable  so what

    P3a: concede newspaper


    Prakken example dialogue7
    Prakken: example dialogue

    P1: claim safe

    O1: why safe

    P2: safe since airbag,

    airbag  safe

    O2b: safe since newspaper,

    newspaper  safe

    O2a: concede airbag

    O3: safe since high speed,

    high speed  safe

    P3b: so whatsince unreliable,

    unreliable  so what

    P3a: concede newspaper


    Prakken example dialogue8
    Prakken: example dialogue

    P1: claim safe

    O1: why safe

    P4: retract safe

    P2: safe since airbag,

    airbag  safe

    O2b: safe since newspaper,

    newspaper  safe

    O2a: concede airbag

    O3: safe since high speed,

    high speed  safe

    P3b: so whatsince unreliable,

    unreliable  so what

    P3a: concede newspaper


    Argument graph

    safe

    airbag  safe

    airbag

    safe

    safe

    newspaper  safe

    high speed  safe

    newspaper

    high speed

    Argument graph

    so what

    unreliable

    unreliable  so what


    Winning and logic
    Winning and logic

    • A protocol should respect the underlying logic

    • We want: main claim is in iff it is implied by the exchanged information

      • (except information that is disputed and not defended)

    • Ensured in relevant protocols (under certain conditions)


    Prakken s relevant protocols characteristics
    Prakken’s relevant protocols: characteristics

    • Protocol

      • Multiple-move

      • Multiple-reply

      • Not deterministic in Lc

      • Immediate-response

    • Dialogues

      • Can be long (stepwise construction of arguments, alternative replies

      • Both sides can develop arguments

    • Logic

      • Used for single agent: construct/attack arguments

      • Used for outcome: players jointly build dialectical graph


    Filibustering
    Filibustering

    • Many two-party protocols allow obstructive behaviour:

      • P: claim p

      • O: why p?

      • P: p since q

      • O: why q?

      • P: q since r

      • O: why r?

      • ...


    Possible sanctions
    Possible sanctions

    • Social sanctions:

      • I don’t talk to you any more

    • Shift of burden of proof by third party

      • ...

      • P: q since r

      • O: why r?

      • referee: O, you must defend not-r!


    Protocol design vs agent design
    Protocol design vs. agent design

    • Can protocol designer rely on agent properties?

      • Rationality

      • Cooperativeness

      • Social behaviour


    Design of dialogical agents
    Design of dialogical agents

    • Assertion and acceptance attitudes (PWA)

    • Model choice of move as planning / practical reasoning

      • Amgoud 2006

    • Apply game theory

      • Roth 2007

    • Much work remains to be done


    Investigation of protocol properties formal proof of experimentation
    Investigation of protocol properties(formal proof of experimentation)

    • Does protocol induce “well-behaved” dialogues? (is it fair and effective?)

    • Do agent attitudes, external goals or social conventions induce “well-behaved” dialogues?

    • If a claim is successfully defended, is it implied by

      • The shared or joint commitments of all participants?

      • The shared or joint beliefs of all participants?

    • Do agent attitudes constrain or even predetermine the outcome?


    R esearch issues
    Research issues

    • Investigation of protocol properties

    • Combinationsof dialogue types

      • Deliberation!

    • Multi-party dialogues

    • Protocol design vs agent design

    • Embedding in social context

    • A framework for dialogue games


    Further reading
    Further reading

    • Argumentation in logic

      • H. Prakken & G. Vreeswijk, Logics for defeasible argumentation (Handbook of Philosophical Logic, 2nd edition)

    • Argumentation in dialogue

      • H. Prakken, Formal systems for persuasion dialogue. The Knowledge Engineering Review 21:163-188, 2006.

      • I. Rahwan et al., Argumentation-based negotiation, The Knowledge Engineering Review 18:343-375, 2003.

    • For more resources see:http://www.cs.uu.nl/people/henry/easss07.html


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