cerutti--aaai fall symposia 2009

University of BresciaDipartimento di Elettronica per l'Automazione

Knowledge Engineering and Human-Computer Interaction Research Group

© 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

An Argumentation-based An Argumentation-based Approach to Modelling Decision Approach to Modelling Decision Support Contexts with What-If Support Contexts with What-If

CapabilitiesCapabilities

Pietro Baroni, Federico Cerutti, Massimiliano Giacomin and Giovanni GuidaPietro Baroni, Federico Cerutti, Massimiliano Giacomin and Giovanni Guida

AAAI 2009 Fall Symposium SeriesThe Uses of Computational Argumentation

Arlington, November, 5, 2009

Slide 2 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

“Good advice”

The advice should be presented in a form which can be readily understood by decision makers

There should be ready access to both information and reasoning underpinning the advice

If decision support involves details which are unusual to the decision maker, it is of primary importance that s/he can discuss these details with his advisor

Girle et al., 2003

Slide 3 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Transparency about the advice

Practical reasoningabout “what to do”

Knowledgerepresentation

Computation ofoutcomes

© 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Knowledge representationKnowledge representation➢ Computation of outcomes

➢ Conclusions and future works

© 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Argument (and attack) schemes

Use of argument scheme to represent the knowledge Structure which contains the information in favour of

a given conclusion

Introduction of a possible modelling of conflicts by “attack scheme”

Structure which contains the information in favour of a given conflict

© 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

The main concepts

Circumstance: a state of the world Fact: a particular circumstance assumed to be true Goal: a state of the world we want to achieve Action: support for the achievement of a goal Preference: “[…] a greater liking for one alternative

over another or others […]” Value: “Worth or worthiness […] in respect of rank

or personal qualities” Must Value: a value that we commit to promote

Slide 7 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Example (1)

Treatment for a patient threatened by blood clotting Goal: obtaining a low platelet adhesion The available knowledge base concerning

treatments: Administer Aspirin (value of Safety) Administer Chlopidogrel (value of Safety) Do nothing (value of Cost)

Slide 8 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

PAS: A2Circumstances: given patient's situationAction: we should administer aspirinGoal: reducing blood clottingValue: SafetySign: +

Formal counterpart (1)Practical Args (from Atkinson et al.)

Slide 9 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (1)The Attacks among PAS

PAtS1: αSource: A1Target: A2Conditions:A1.action and A2.action are incompatible

Slide 10 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

VAS: V1Value: Cost

Formal counterpart (1)The Values

Slide 11 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (1)The Defences from the Values

VDeS1: βSource: V2Target: αConditions:α.target.value = V2.value, α.source.value ≠ V2.value

PAtS1: α…

Slide 12 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (1)The Defences from the Values

VDeS1: βSource: V2Target: αConditions:α.target.value = V2.value, α.source.value ≠ V2.value

VDeS2: γSource: V1Target: βConditions:β.source ≠ V1, β.target.source.value ≠ V1.value

PAtS1: α…

Slide 13 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (1)The Defences from the Values

VDeS1: βSource: V2Target: αConditions:α.target.value = V2.value, α.source.value ≠ V2.value

VDeS2: γSource: V1Target: βConditions:β.source ≠ V1, β.target.source.value ≠ V1.valueVDefence: β

Defending: A2Defended: V2

VDefence: γDefending: A1Defended: V1

PAtS1: α…

Slide 14 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Example (2)

From patient's file we learn that he has a history of gastritis

Then we should not administer Aspirin without a proton pump inhibitor

In fact, it gives rise to risk of ulceration And it will demote the value of Safety As far as we know, no proton pump inhibitor is

available

Slide 15 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (2)A PAS with negative sign...

PAS: A4Circumstances: proton pump unavailableAction: we should not administer aspirinGoal: risk of ulcerationValue: SafetySign: -

Slide 16 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (2)...and the relative attacks

PAtS2: δSource: A4Target: A2Conditions:A4.action = ¬ A2.action

Slide 17 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (2)...and the relative attacks

VAAtS: εSource: A4Target: βConditions: A4.circumstance = β.defended.circumstance, A4.action = ¬ β.defended.action, A4.goal = β.defended.goal, A4.value = β.defended.value, A4.sign = -, β.defended.sign = +

PAtS2: δSource: A4Target: A2Conditions:A4.action = ¬ A2.action

Slide 18 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Example (3)

Suppose now that the assumption that no proton pump inhibitor is available reveals to be false

Suppose also that between aspirin and chlopidogrel a doctor prefers to administer aspirin because it is in stock and immediately available

Slide 19 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

FAS: A5Circumstances: a proton pump is available

Formal counterpart (3)A Fact

Slide 20 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (3)An “undercut”

FAtS: ζSource: A5Target: A4Conditions: A5.circumstances= ¬ A4.circumstances

Slide 21 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

PRAS: P1Preferred: A2Notpreferred: A3

Formal counterpart (3)A preference

Slide 22 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (3)The greater liking

PAtS: η...

FAtS: θSource: P1Target: ηConditions: P1.preferred = η.target, P1.notpreferred = η.source

Slide 23 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Example (4)

Determine the ultimate decision outcome Achieve the goal of reducing blood clotting It promotes the value of Safety We must promote the value of Safety

Slide 24 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

MAS: MV2Value: Safety

Formal counterpart (4)The Must Value

Slide 25 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Formal counterpart (4)What-If Scenario

MAtS2: κSource: MV2Target: γConditions: MV2.value = γ.target.source.value,MV2.value ≠ γ.source.value

VDeS2: γ...

Slide 26 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Small SummaryArgument Scheme Taxonomy

Practical Argument Scheme Factual Argument Scheme Value Argument Scheme Preference Argument Scheme Must Argument Scheme

Slide 27 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

In the example

Slide 28 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Small SummaryAttack Scheme Taxonomy (1)

PAtS1: incompatible actions PAtS2: “rebuttal” VAtS : incompatible values VDefence (VDeS[1-2]): a value protects both the

arguments which promote it and the attacks sourced from that arguments

VAAtS: if a practical argument P suggests not to perform an action A since it demotes a value V, if P will be considered acceptable, then V cannot defend the argument whose action is A

Slide 29 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

In the example (1)

Slide 30 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Small SummaryAttack Scheme Taxonomy (2)

FAtS: “undercut” PRAtS: someone told us that an attack cannot be

considered since an external preference MAtS1: an instance of Must Argument Scheme has

to protect the related Value argument against the incompatible values

MAtS2: an instance of Must Argument Scheme has to protect the instances of VDefence which start from the related Value argument

Slide 31 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

In the example (2)

© 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Computation of outcomesComputation of outcomes➢ Knowledge representation

➢ Conclusions and future works

Slide 33 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Argumentation Framework for Decision Support Problem

Slide 34 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Argumentation Framework withRecoursive Attacks (AFRA)

Slide 35 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

From AFDSP to AFRA

Slide 36 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

AFRA: Defeat relation

Slide 37 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

AFRA: Admissibility

Slide 38 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

AFRA: Preferred Extension

Slide 39 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Recalling the example...

Slide 40 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

...and the preferred extension

© 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Conclusions and Conclusions and future worksfuture works

➢ Knowledge representation➢ Computation of outcomes

Slide 42 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Conclusions

Preliminary investigation about formalisation of decision support problems

Three main contributions: The role of attack schemes Attacks to attacks in practice Support to “What-if” reasoning

Slide 43 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Future works

Knowledge representation: Enhancing attacks schemes Ontological status of attacks Multiple What-if Situations

Computation of outcomes Further investigation on the theoretical bases of AFRA Argumentation semantics in this context

Slide 44 © 2009 Federico Cerutti <federico.cerutti@ing.unibs.it>

Open questions

The notion of attack scheme: soundness and usefulness

Attack schemes and critical questions What-if only w.r.t. Values