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Transcript of Commonsense Reasoning and Argumentation 14/15 HC 13: Dialogue Systems for Argumentation (1) Henry...
Commonsense Reasoning and Argumentation 14/15
HC 13: Dialogue Systems for
Argumentation (1)
Henry Prakken25 March 2015
Why do agents need argumentation?
For their internal reasoning Reasoning about beliefs, goals, intentions
etc often is defeasible For their interaction with other agents
Information exchange involves explanation Collaboration and negotiation involve
conflict of opinion and persuasion
Overview Dialogue systems for argumentation
Inference vs. dialogue Use of argumentation in MAS General ideas Two systems (1)
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Prof. P says that …
Prof. P has political ambitions
People with political ambitions are not objective
Prof. P is not objective
Increased inequality is good
Increased inequality stimulates competition
Competition is good
USA lowered taxes but productivity decreased
We should lower taxes
claim
We should lower taxes
claim why
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
since
claim why
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
since since
claim why
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Increased inequality is good
since since
claim why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Increased inequality is good
since since
claim why
why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Increased inequality is good
Increased inequality stimulates competition
Competition is good
since since
since
claim why
why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Increased inequality is good
Increased inequality stimulates competition
Competition is good
since since
since
claim
claim
why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Increased inequality is good
Increased inequality stimulates competition
Competition is good
since since
since
claim
claim
why
why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Increased inequality is good
Increased inequality stimulates competition
Competition is good
USA lowered taxes but productivity decreased
since
since since
since
claim
claim
why
why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Increased inequality is good
Increased inequality stimulates competition
Competition is good
USA lowered taxes but productivity decreased
since
since since
since
claim
claim
why
why
why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Prof. P says that …
Increased inequality is good
Increased inequality stimulates competition
Competition is good
USA lowered taxes but productivity decreased
since
since since
since
since
claim
claim
why
why
why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Prof. P says that …
Prof. P has political ambitions
People with political ambitions are not objective
Prof. P is not objective
Increased inequality is good
Increased inequality stimulates competition
Competition is good
USA lowered taxes but productivity decreased
since
since since
since since
since
claim
claim
why
why
why
claim
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Prof. P says that …
Prof. P has political ambitions
People with political ambitions are not objective
Prof. P is not objective
Increased inequality is good
Increased inequality stimulates competition
Competition is good
USA lowered taxes but productivity decreased
since
since since
since since
since
claim
claim
why
why
why
claim
concede
We should lower taxes
Lower taxes increase productivity
Increased productivity is good
We should not lower taxes
Lower taxes increase inequality
Increased inequality is bad
Lower taxes do not increase productivity
Prof. P says that …
Prof. P has political ambitions
People with political ambitions are not objective
Prof. P is not objective
Increased inequality is good
Increased inequality stimulates competition
Competition is good
USA lowered taxes but productivity decreased
since
since since
since since
since
claim
claim
why
why
why
retract
claim
concede
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
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 goodO: since French cars are unsafeO: since magazine Meinwagen says soO: 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) 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 goodO: since French cars are unsafeO: since magazine Meinwagen says soO: 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) 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 goodO: since French cars are unsafeO: since magazine Meinwagen says soO: 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.
Inference vs dialogue
Dialogue systems for argumentation have: A communication language (well-formed utterances) A protocol (which utterances are allowed at which
point?) Termination and outcome rules
Argument games are a proof theory for a logic
But real argumentation dialogues have real players!
Distributed information Richer communication languages Dynamics
Standards for argumentation formalisms
Logical argument games: soundness and completeness wrt some semantics of an argumentation logic
Dialogue systems: effectiveness wrt dialogue goal and fairness wrt participants’ goals
Argumentation: Dialogue goal = rational resolution of conflicts of opinion Participants’ goal = to persuade
Argumentation is often instrumental to other dialogue types
Does argumentation promote the goals of e.g. negotiation or deliberation?
Some properties of dialogue systems that can be studied
Correspondence of outcome with players’ beliefs If the union of participants’ beliefs justifies
p, can/will agreement on p result? (‘completeness’)
If participants’ agree on p, does the union of their beliefs justify p? (‘soundness’)
Disregarding vs. assuming participants’ personalities
Game for grounded semantics unsound in distributed settings
Paul: p, r
Olga: s,t
p qs qr sr,t p
Knowledge bases Inference rules
P1: q since p
Game for grounded semantics unsound in distributed settings
Paul: p, r
Olga: s,t
Knowledge bases Inference rules
P1: q since p
O1: q since s
p qs qr sr,t p
Game for grounded semantics unsound in distributed settings
Paul: p, r
Olga: s,t, r
Knowledge bases Inference rules
P1: q since p
O1: q since s
P2: s since r
p qs qr sr,t p
Game for grounded semantics unsound in distributed settings
Paul: p, r
Olga: s,t, r
Knowledge bases Inference rules
P1: q since p
O1: q since s
O2: p since r,t
P2: s since r
p qs qr sr,t p
Example 1
Paul: r
Olga: s
p qr ps r
Knowledge bases Inference rules
P1: q since p
Paul Olga does not justify q but they could
agree on q
Olga is credulous: she concedes everything for
which she cannot construct a (defensible or justified) counterargument
Example 1
Paul: r
Olga: s
p qr ps r
Knowledge bases Inference rules
P1: q since p
Paul Olga does not justify q but they could
agree on q
O1: concede p,q
Example 1
Paul: r
Olga: s
p qr ps r
Knowledge bases Inference rules
P1: q since p
Paul Olga does not justify q but they could
agree on q
Olga is sceptical: she challenges everything for
which she cannot construct a (defensible or justified)
argument
Example 1
Paul: r
Olga: s
Knowledge bases Inference rules
P1: q since p
O1: why p?
p qr ps r
Paul Olga does not justify q but they could
agree on q
Example 1
Paul: r
Olga: s
Knowledge bases Inference rules
P1: q since p
O1: why p?
P2: p since r
p qr ps r
Paul Olga does not justify q but they could
agree on q
Example 1
Paul: r
Olga: s
Knowledge bases Inference rules
P1: q since p
O1: why p?
O2: r since s
P2: p since r
p qr ps r
Paul Olga does not justify q but they could
agree on q
Example 2
Paul: pq
Olga: pq p
Knowledge bases Inference rules
P1: claim pModus ponens
…
Paul Olga does not justify p but they will agree on p if players are
conservative, that is, if they stick to their beliefs if possible
Example 2
Paul: pq
Olga: pq p
Knowledge bases Inference rules
P1: claim p
O1: concede p
Modus ponens
…
Paul Olga does not justify p but they will agree on p if players are
conservative, that is, if they stick to their beliefs if possible
Example 2
Paul: pq
Olga: pq p
Knowledge bases Inference rules
P1: claim p
O1: what about q?
Modus ponens
…
Possible solution (for open-minded agents, who are
prepared to critically test their beliefs):
Example 2
Paul: pq
Olga: pq p
Knowledge bases Inference rules
P1: claim p
O1: what about q?
Modus ponens
…
P2: claim q
Possible solution (for open-minded agents, who are
prepared to critically test their beliefs):
Example 2
Paul: pq
Olga: pq p
Knowledge bases Inference rules
P1: claim p
O1: what about q?
Modus ponens
…
P2: claim q
O2: p since q, q p Possible solution (for open-minded agents, who are
prepared to critically test their beliefs):
Problem: how to ensure relevance?
Dialogue game systems in more detail
A dialogue purpose Participants (with roles) A topic language Lt
With a logic A communication language Lc
With a protocol Move legality rules Effect rules for Lc (“commitment rules”) Turntaking rules Termination and outcome rules
Effect rules Specify commitments
“Claim p” and “Concede p” commits to p “p since Q” commits to p and Q “Retract p” ends commitment to p ...
Commitments used for: Determining outcome Enforcing ‘dialogical consistency’ ...
Public semantics for dialogue protocols
Public semantics: can protocol compliance be externally observed?
Commitments are 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”
More and less strict protocols Single-multi move: one or more moves
per turn allowed Single-multi-reply: one or more replies
to the same move allowed Deterministic: no choice from legal
moves Deterministic in Lc: no choice from
speech act types Only reply to moves from previous turn?
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
Lc: Claim p, Why p, Concede p, Claim S p Lt, S Lt
Lt: propositional Logic: argumentation logic
Arguments: (S, p) such that S Lt, consistent S propositionally implies p
Defeat: (S, p) defeats (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
Assertion/Acceptance attitudes
Relative to speaker’s own KB + hearer’s commitments Confident/Credulous agent: can assert/accept P
iff she can construct an argument for P Careful/Cautious agent: can assert/accept P iff
she can construct an argument for P and no stronger argument for -P
Thoughtful/Skeptical agent: can assert/accept P iff she can construct a justified argument for P
If part of protocol, then protocol has no public semantics!
PWA: protocol1. W claims p;2. B concedes if allowed by its attitude, if not claims -p if allowed
by its attitude or else challenges p3. If B claims -p, then goto 2 with players’ roles reversed and -p
in place of p;4. If B has challenged, then:
a. W claims S, an argument for p;b. Goto 2 for each s S in turn.
5. B concedes p if allowed by its attitude, or the dialogue terminates without agreement.
Also: - no player repeats its own moves - if the ‘indicated’ move cannot be made (i.e., would repeat
a move), the dialogue terminates
Outcome: do players agree at termination?
The agents’ KBs
P:
airbagairbag safe
O:
newspapernewspaper safe
PWA: example dialogue (1)
P: thoughtful/skepticalP1: claim safe
O: careful/cautious
P:
airbagairbag safe
O:
newspapernewspaper safe
PWA: example dialogue (1)
P: thoughtful/skepticalP1: claim safe
O: careful/cautious
P:
airbagairbag safe
O:
newspapernewspaper safe+ safe
PWA: example dialogue (1)
P: thoughtful/skepticalP1: claim safe
O: careful/cautiousO1: concede safe
P:
airbagairbag safe
O:
newspapernewspaper safe+ safe
PWA: example dialogue (2)
P: thoughtful/skepticalP1: claim safe
O: thoughtful/skeptical
P:
airbagairbag safe
O:
newspapernewspaper safe+ safe
PWA: example dialogue (2)
P: thoughtful/skepticalP1: claim safe
O: thoughtful/skepticalO1: why safe
P:
airbagairbag safe
O:
newspapernewspaper safe+ safe
PWA: example dialogue (2)
P: thoughtful/skepticalP1: claim safe P2: claim {airbag, airbag
safe}
O: thoughtful/skepticalO1: why safe
P:
airbagairbag safe
O:
newspapernewspaper safeP1: + safeP2: + airbag, airbag safe
PWA: example dialogue (2)
P: thoughtful/skepticalP1: claim safe P2: claim {airbag, airbag
safe}
O: thoughtful/skepticalO1: why safeO2: why airbag
P:
airbagairbag safe
O:
newspapernewspaper safeP1: + safeP2: + airbag, airbag safe
PWA: example dialogue (2)
P: thoughtful/skepticalP1: claim safe P2: claim {airbag, airbag
safe}P3: claim {airbag}
O: thoughtful/skepticalO1: why safeO2: why airbag
P:
airbagairbag safe
O:
newspapernewspaper safeP1: + safeP2: + airbag, airbag safe
PWA: example dialogue (2)
P: thoughtful/skepticalP1: claim safe P2: claim {airbag, airbag
safe}P3: claim {airbag}
O: thoughtful/skepticalO1: why safeO2: why airbag
O3: why airbag safe
P:
airbagairbag safe
O:
newspapernewspaper safeP1: + safeP2: + airbag, airbag safe
PWA: example dialogue (2)
P: thoughtful/skepticalP1: claim safe P2: claim {airbag, airbag
safe}P3: claim {airbag}P2: claim {airbag safe}
O: thoughtful/skepticalO1: why safeO2: why airbag
O3: why airbag safe
P:
airbagairbag safe
O:
newspapernewspaper safeP1: + safeP2: + airbag, airbag safe
PWA: example dialogue (3)
P: thoughtful/skepticalP1: claim safe
O: confident/skeptical
P:
airbagairbag safe
O:
newspapernewspaper safe+ safe
PWA: example dialogue (3)
P: thoughtful/skepticalP1: claim safe P2: why safe
O: confident/skepticalO1: claim safe
P:
airbagairbag safeO1: + safe
O:
newspapernewspaper safeP1: + safe
PWA: example dialogue (3)
P: thoughtful/skepticalP1: claim safe P2: why safe
P3a: why newspaperP3b: why newspaper safe
O: confident/skepticalO1: claim safeO2: claim {newspaper, newspaper
safe}O3a: claim {newspaper}O3b: claim {newspaper
safe}P:
airbagairbag safeO1: + safe O2: + newspaper, newspaper safe
O:
newspapernewspaper safeP1: + safe
PWA: characteristics Protocol
multi-move (if 4a is breadth-first) (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 Commmitments
Used for attitudes and outcome