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A Translation-based Approach for Revision of Argumentation Frameworks

Sylvie Coste-Marquis S´ebastien Konieczny Jean-Guy Mailly Pierre Marquis

Centre de Recherche en Informatique de Lens Universit´e d’Artois – CNRS UMR 8188

14th European Conference on Logics in Artificial Intelligence September 24th - 26th – Madeira

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Schematic Explanation of the Approach

I F: an argumentation framework

I σ: a semantics to define acceptable arguments

I ϕ: a propositional formula indicating how to reviseF

F, σ, ϕ

F ? ϕ

F encoded Revision ofF encoded σ-encoding

?

σ-decoding

AGM Revision AF Revision

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Schematic Explanation of the Approach

I F: an argumentation framework

I σ: a semantics to define acceptable arguments

I ϕ: a propositional formula indicating how to reviseF

F, σ, ϕ F ? ϕ

F encoded Revision ofF encoded σ-encoding

?

σ-decoding

AGM Revision AF Revision

2/25 AMANDE

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Schematic Explanation of the Approach

I F: an argumentation framework

I σ: a semantics to define acceptable arguments

I ϕ: a propositional formula indicating how to reviseF

F, σ, ϕ F ? ϕ

F encoded

Revision ofF encoded

σ-encoding

?

σ-decoding

AGM Revision AF Revision

2/25 AMANDE

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Schematic Explanation of the Approach

I F: an argumentation framework

I σ: a semantics to define acceptable arguments

I ϕ: a propositional formula indicating how to reviseF

F, σ, ϕ F ? ϕ

F encoded Revision ofF encoded σ-encoding

?

σ-decoding

AGM Revision AF Revision

2/25 AMANDE

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Schematic Explanation of the Approach

I F: an argumentation framework

I σ: a semantics to define acceptable arguments

I ϕ: a propositional formula indicating how to reviseF

F, σ, ϕ F ? ϕ

F encoded Revision ofF encoded σ-encoding

?

σ-decoding

AGM Revision

AF Revision

2/25 AMANDE

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Schematic Explanation of the Approach

I F: an argumentation framework

I σ: a semantics to define acceptable arguments

I ϕ: a propositional formula indicating how to reviseF

F, σ, ϕ F ? ϕ

F encoded Revision ofF encoded σ-encoding

?

σ-decoding

AGM Revision

AF Revision

2/25 AMANDE

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Schematic Explanation of the Approach

I F: an argumentation framework

I σ: a semantics to define acceptable arguments

I ϕ: a propositional formula indicating how to reviseF

F, σ, ϕ F ? ϕ

F encoded Revision ofF encoded σ-encoding

?

σ-decoding

AGM Revision

AF Revision

2/25 AMANDE

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Schematic Explanation of the Approach

I F: an argumentation framework

I σ: a semantics to define acceptable arguments

I ϕ: a propositional formula indicating how to reviseF

F, σ, ϕ F ? ϕ

F encoded Revision ofF encoded σ-encoding

?

σ-decoding

AGM Revision AF Revision

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Plan

Introduction

Abstract Argumentation Belief Revision

Translation-based Revision Encoding

Distance-based Operators and Minimal Change Characterization of Operators in theacc Case Extensions of the Method

Conclusion and Future Work

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Abstract Argumentation [Dung 1995]

I An abstract argumentation framework is a pair hA,Ri with R ⊆ A × A:

a b c

I An extension is a set of arguments that can be accepted together

I Different semantics to define the extensions: complete, stable, preferred, grounded, etc.

I The aim is to know whether an argument is accepted or not w.r.t. the chosen semantics σ

I An argumenta∈ Ais (skeptically) accepted iff it belongs to every extension of the AF w.r.t. the considered semanticsσ:

F|∼σaa\

Extσ(F)

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AGM framework for Belief Revision

I Principles of Belief Revision:

I Primacy of update

I Consistency

I Minimal change

I Set of postulates: characterizes the “good” operators

[Alchourr´on, G¨ardenfors and Makinson 1985],[Katsuno et Mendelzon 1991] I Representation theorem: “An operator satisfies the postulates

iff it belongs to a particular class”

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AGM framework for Belief Revision

I Principles of Belief Revision:

I Primacy of update

I Consistency

I Minimal change

I Set of postulates: characterizes the “good” operators

[Alchourr´on, G¨ardenfors and Makinson 1985],[Katsuno et Mendelzon 1991] I Representation theorem: “An operator satisfies the postulates

iff it belongs to a particular class”

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AGM framework for Belief Revision

I Principles of Belief Revision:

I Primacy of update

I Consistency

I Minimal change

I Set of postulates: characterizes the “good” operators

[Alchourr´on, G¨ardenfors and Makinson 1985],[Katsuno et Mendelzon 1991] I Representation theorem: “An operator satisfies the postulates

iff it belongs to a particular class”

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AGM framework for Belief Revision

I Principles of Belief Revision:

I Primacy of update

I Consistency

I Minimal change

I Set of postulates: characterizes the “good” operators

[Alchourr´on, G¨ardenfors and Makinson 1985],[Katsuno et Mendelzon 1991] I Representation theorem: “An operator satisfies the postulates

iff it belongs to a particular class”

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AGM framework for Belief Revision

I Principles of Belief Revision:

I Primacy of update

I Consistency

I Minimal change

I Set of postulates: characterizes the “good” operators

[Alchourr´on, G¨ardenfors and Makinson 1985],[Katsuno et Mendelzon 1991]

I Representation theorem: “An operator satisfies the postulates iff it belongs to a particular class”

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AGM framework for Belief Revision

I Principles of Belief Revision:

I Primacy of update

I Consistency

I Minimal change

I Set of postulates: characterizes the “good” operators

[Alchourr´on, G¨ardenfors and Makinson 1985],[Katsuno et Mendelzon 1991]

I Representation theorem: “An operator satisfies the postulates iff it belongs to a particular class”

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AFs Revision

I Aim: Incorporation of a new piece of information about the attack relation and/or the acceptance statuses of arguments

I Two kind of minimal change:

Attack 6= Acceptance

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Propositional Language

I ∀x ∈A,acc(x) = x is skeptically accepted by F

I ∀x,y ∈A,att(x,y) =x attacksy in F

I PropA ={acc(x)|x ∈A} ∪ {att(x,y)|x,y ∈A}

I LA is the propositional language built on the set of variables PropA and the connectives¬,∨,∧

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Encoding an AF

σ-formula of F

Given an AFF =hA,Ri and a semanticsσ, theσ-formula ofF is fσ(F) = ^

(x,y)∈R

att(x,y)∧ ^

(x,y)6∈R

¬att(x,y)

∧thσ(A)

where theσ-theory ofA thσ(A) is a formula which encodes the semanticsσ.

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Encoding an AF

σ-formula of F

Given an AFF =hA,Ri and a semanticsσ, theσ-formula ofF is fσ(F) = ^

(x,y)∈R

att(x,y)∧ ^

(x,y)6∈R

¬att(x,y) ∧thσ(A)

where theσ-theory ofA thσ(A) is a formula which encodes the semanticsσ.

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Encoding the Stable Semantics (1)

Stable extensions of an AF F =hA,Ri [Besnard and Doutre 2004]

^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)

Example

F1= a b c d One stable extension: {a,c}

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Encoding the Stable Semantics (1)

Stable extensions of an AF F =hA,Ri [Besnard and Doutre 2004]

^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)

Example

F1= a b c d One stable extension: {a,c}

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Encoding the Stable Semantics (2)

Skeptical acceptance of an argument ai

|= (^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai)

equivalent to

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai)

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Encoding the Stable Semantics (2)

Skeptical acceptance of an argument ai

|= (^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai) equivalent to

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai)

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Encoding the Stable Semantics (3)

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai)

I Knowledge of the AF is required a priori

I We useatt(x,y) to relax this requirement

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b∈A

(att(b,a)⇒ ¬b))⇒ai)

Stable theory of the set A thst(A) = V

ai∈A(acc(ai)⇔ ∀a1, . . . ,an, (V

a∈A(a⇔V

b∈A(att(b,a)⇒ ¬b))⇒ai))

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Encoding the Stable Semantics (3)

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai)

I Knowledge of the AF is required a priori

I We useatt(x,y) to relax this requirement

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b∈A

(att(b,a)⇒ ¬b))⇒ai)

Stable theory of the set A thst(A) = V

ai∈A(acc(ai)⇔ ∀a1, . . . ,an, (V

a∈A(a⇔V

b∈A(att(b,a)⇒ ¬b))⇒ai))

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Encoding the Stable Semantics (3)

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai)

I Knowledge of the AF is required a priori

I We useatt(x,y) to relax this requirement

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b∈A

(att(b,a)⇒ ¬b))⇒ai)

Stable theory of the set A thst(A) = V

ai∈A(acc(ai)⇔ ∀a1, . . . ,an, (V

a∈A(a⇔V

b∈A(att(b,a)⇒ ¬b))⇒ai))

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Encoding the Stable Semantics (3)

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai)

I Knowledge of the AF is required a priori

I We useatt(x,y) to relax this requirement

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b∈A

(att(b,a)⇒ ¬b))⇒ai)

Stable theory of the set A thst(A) = V

ai∈A(acc(ai)⇔ ∀a1, . . . ,an, (V

a∈A(a⇔V

b∈A(att(b,a)⇒ ¬b))⇒ai))

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Encoding the Stable Semantics (3)

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b:(b,a)∈R

¬b)⇒ai)

I Knowledge of the AF is required a priori

I We useatt(x,y) to relax this requirement

∀a1, . . . ,an,(^

a∈A

(a⇔ ^

b∈A

(att(b,a)⇒ ¬b))⇒ai)

Stable theory of the set A thst(A) = V

ai∈A(acc(ai)⇔∀a1, . . . ,an, (V

a∈A(a⇔V

b∈A(att(b,a)⇒ ¬b))⇒ai))

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Example

F1 = a b c d

thst(A) =

acc(a)⇔ ∀a,b,c,d,[[(a⇔((att(a,a)⇒ ¬a)∧(att(b,a)⇒ ¬b)

∧(att(c,a)⇒ ¬c)∧(att(d,a)⇒ ¬d)))

∧(b⇔((att(a,b)⇒ ¬a)∧(att(b,b)⇒ ¬b)

∧(att(c,b)⇒ ¬c)∧(att(d,b)⇒ ¬d)))

∧(c ⇔((att(a,c)⇒ ¬a)∧(att(b,c)⇒ ¬b)

∧(att(c,c)⇒ ¬c)∧(att(d,c)⇒ ¬d)))

∧(d ⇔((att(a,d)⇒ ¬a)∧(att(b,d)⇒ ¬b)

∧(att(c,d)⇒ ¬c)∧(att(d,d)⇒ ¬d)))]⇒a]

∧ acc(b)⇔ ∀a,b,c,d,[· · · ⇒b]

∧ acc(c)⇔ ∀a,b,c,d,[· · · ⇒c]

∧ acc(d)⇔ ∀a,b,c,d,[· · · ⇒d]

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Example

F1 = a b c d

thst(A) =

acc(a)⇔ ∀a,b,c,d,[[(a⇔((att(a,a)⇒ ¬a)∧(att(b,a)⇒ ¬b)

∧(att(c,a)⇒ ¬c)∧(att(d,a)⇒ ¬d)))

∧(b⇔((att(a,b)⇒ ¬a)∧(att(b,b)⇒ ¬b)

∧(att(c,b)⇒ ¬c)∧(att(d,b)⇒ ¬d)))

∧(c ⇔((att(a,c)⇒ ¬a)∧(att(b,c)⇒ ¬b)

∧(att(c,c)⇒ ¬c)∧(att(d,c)⇒ ¬d)))

∧(d ⇔((att(a,d)⇒ ¬a)∧(att(b,d)⇒ ¬b)

∧(att(c,d)⇒ ¬c)∧(att(d,d)⇒ ¬d)))]⇒a]

∧ acc(b)⇔ ∀a,b,c,d,[· · · ⇒b]

∧ acc(c)⇔ ∀a,b,c,d,[· · · ⇒c]

∧ acc(d)⇔ ∀a,b,c,d,[· · · ⇒d]

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Example

F1 = a b c d

thst(A) =

acc(a)⇔ ∀a,b,c,d,[[(a⇔((att(a,a)⇒ ¬a)∧(att(b,a)⇒ ¬b)

∧(att(c,a)⇒ ¬c)∧(att(d,a)⇒ ¬d)))

∧(b⇔((att(a,b)⇒ ¬a)∧(att(b,b)⇒ ¬b)

∧(att(c,b)⇒ ¬c)∧(att(d,b)⇒ ¬d)))

∧(c ⇔((att(a,c)⇒ ¬a)∧(att(b,c)⇒ ¬b)

∧(att(c,c)⇒ ¬c)∧(att(d,c)⇒ ¬d)))

∧(d ⇔((att(a,d)⇒ ¬a)∧(att(b,d)⇒ ¬b)

∧(att(c,d)⇒ ¬c)∧(att(d,d)⇒ ¬d)))]⇒a]

∧ acc(b)⇔ ∀a,b,c,d,[· · · ⇒b]

∧ acc(c)⇔ ∀a,b,c,d,[· · · ⇒c]

∧ acc(d)⇔ ∀a,b,c,d,[· · · ⇒d]

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Example

F1 = a b c d

thst(A) =

acc(a)⇔ ∀a,b,c,d,[[(a⇔((att(a,a)⇒ ¬a)∧(att(b,a)⇒ ¬b)

∧(att(c,a)⇒ ¬c)∧(att(d,a)⇒ ¬d)))

∧(b⇔((att(a,b)⇒ ¬a)∧(att(b,b)⇒ ¬b)

∧(att(c,b)⇒ ¬c)∧(att(d,b)⇒ ¬d)))

∧(c ⇔((att(a,c)⇒ ¬a)∧(att(b,c)⇒ ¬b)

∧(att(c,c)⇒ ¬c)∧(att(d,c)⇒ ¬d)))

∧(d ⇔((att(a,d)⇒ ¬a)∧(att(b,d)⇒ ¬b)

∧(att(c,d)⇒ ¬c)∧(att(d,d)⇒ ¬d)))]⇒a]

∧ acc(b)⇔ ∀a,b,c,d,[· · · ⇒b]

∧ acc(c)⇔ ∀a,b,c,d,[· · · ⇒c]

∧ acc(d)⇔ ∀a,b,c,d,[· · · ⇒d]

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Example

F1 = a b c d

thst(A) =

acc(a)⇔ ∀a,b,c,d,[[(a⇔((att(a,a)⇒ ¬a)∧(att(b,a)⇒ ¬b)

∧(att(c,a)⇒ ¬c)∧(att(d,a)⇒ ¬d)))

∧(b⇔((att(a,b)⇒ ¬a)∧(att(b,b)⇒ ¬b)

∧(att(c,b)⇒ ¬c)∧(att(d,b)⇒ ¬d)))

∧(c ⇔((att(a,c)⇒ ¬a)∧(att(b,c)⇒ ¬b)

∧(att(c,c)⇒ ¬c)∧(att(d,c)⇒ ¬d)))

∧(d ⇔((att(a,d)⇒ ¬a)∧(att(b,d)⇒ ¬b)

∧(att(c,d)⇒ ¬c)∧(att(d,d)⇒ ¬d)))]⇒a]

∧ acc(b)⇔ ∀a,b,c,d,[· · · ⇒b]

∧ acc(c)⇔ ∀a,b,c,d,[· · · ⇒c]

∧ acc(d)⇔ ∀a,b,c,d,[· · · ⇒d]

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Example

F1 = a b c d

I fst(F1) =thst(A)∧V

(a,b)∈Ratt(a,b)∧V

(a,b)6∈R¬att(a,b)

I Propagating the values of theatt(x,y) variables, we get the values of the acc(x):

acc(a) =acc(c) =true and acc(b) =acc(d) =false So the arguments accepted byF1 are:{a,c}

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Reminder

F, σ, ϕ F ? ϕ

fσ(F) fσ(F)◦(ϕ∧thσ(A)) Encoding

?

Decoding

:Projatt(Φ) arg(Modsatt)

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Reminder

F, σ, ϕ F ? ϕ

fσ(F) fσ(F)◦(ϕ∧thσ(A)) Encoding

?

Decoding

:Projatt(Φ) arg(Modsatt)

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Reminder

F, σ, ϕ F ? ϕ

fσ(F) fσ(F)◦(ϕ∧thσ(A)) Encoding

?

Decoding

:Projatt(Φ) arg(Modsatt)

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Reminder

F, σ, ϕ F ? ϕ

fσ(F) fσ(F)◦(ϕ∧thσ(A)) Encoding

?

Decoding:Projatt(Φ) arg(Modsatt)

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Decoding Tools

I Projatt(Φ): projection of the models of Φ on the variables att(x,y)

I arg(Modsatt): generation of AFs from models projected onatt(x,y)

Example of decoding

WithA={a,b}, the revised models could be:

Mod(Φ) ={{acc(a),¬acc(b),¬att(a,a),att(a,b),¬att(b,a),¬att(b,b)}}. So,Projatt(Φ) ={{¬att(a,a),att(a,b),¬att(b,a),¬att(b,b)}}and

arg(Projatt(Φ)) ={F} with F the AF below:

a b

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Decoding Tools

I Projatt(Φ): projection of the models of Φ on the variables att(x,y)

I arg(Modsatt): generation of AFs from models projected onatt(x,y) Example of decoding

WithA={a,b}, the revised models could be:

Mod(Φ) ={{acc(a),¬acc(b),¬att(a,a),att(a,b),¬att(b,a),¬att(b,b)}}.

So,Projatt(Φ) ={{¬att(a,a),att(a,b),¬att(b,a),¬att(b,b)}}and arg(Projatt(Φ)) ={F} with F the AF below:

a b

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Decoding Tools

I Projatt(Φ): projection of the models of Φ on the variables att(x,y)

I arg(Modsatt): generation of AFs from models projected onatt(x,y) Example of decoding

WithA={a,b}, the revised models could be:

Mod(Φ) ={{acc(a),¬acc(b),¬att(a,a),att(a,b),¬att(b,a),¬att(b,b)}}.

So,Projatt(Φ) ={{¬att(a,a),att(a,b),¬att(b,a),¬att(b,b)}}and arg(Projatt(Φ)) ={F} with F the AF below:

a b

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Decoding Tools

I Projatt(Φ): projection of the models of Φ on the variables att(x,y)

I arg(Modsatt): generation of AFs from models projected onatt(x,y) Example of decoding

WithA={a,b}, the revised models could be:

Mod(Φ) ={{acc(a),¬acc(b),¬att(a,a),att(a,b),¬att(b,a),¬att(b,b)}}.

So,Projatt(Φ) ={{¬att(a,a),att(a,b),¬att(b,a),¬att(b,b)}}and arg(Projatt(Φ)) ={F} with F the AF below:

a b

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Translation-based Revision Operator

Translation-based Revision

Let◦ be a KM revision operator. For every semanticsσ, every AF F =hA,Ri and every formula ϕ∈ LA, the associated

translation-based revision operator? is defined by:

F ? ϕ=arg(Projatt(fσ(F)◦(ϕ∧thσ(A))))

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Translation-based Revision Operator

Translation-based Revision

Let◦ be a KM revision operator. For every semanticsσ, every AF F =hA,Ri and every formula ϕ∈ LA, the associated

translation-based revision operator? is defined by:

F ? ϕ=arg(Projatt(fσ(F)◦(ϕ∧thσ(A))))

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Distance-based Revision

Letd be a distance between interpretations on LA. Given a formulaψ∈ LA, the pre-order ≤ψ is defined by:

ω≤ψ ω0 iff d(ω,Mod(ψ))≤d(ω0,Mod(ψ))

The KM revision operator ◦d based ond is defined by: Mod(ψ◦dα) = min(Mod(α),≤ψ)

The AF revision operator ?d based on distance d is defined by: F ?dϕ=arg(Projatt(fσ(F)◦d(ϕ∧thσ(A))))

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Distance-based Revision

Letd be a distance between interpretations on LA. Given a formulaψ∈ LA, the pre-order ≤ψ is defined by:

ω≤ψ ω0 iff d(ω,Mod(ψ))≤d(ω0,Mod(ψ)) The KM revision operator ◦d based ond is defined by:

Mod(ψ◦dα) = min(Mod(α),≤ψ)

The AF revision operator ?d based on distance d is defined by: F ?dϕ=arg(Projatt(fσ(F)◦d(ϕ∧thσ(A))))

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Distance-based Revision

Letd be a distance between interpretations on LA. Given a formulaψ∈ LA, the pre-order ≤ψ is defined by:

ω≤ψ ω0 iff d(ω,Mod(ψ))≤d(ω0,Mod(ψ)) The KM revision operator ◦d based ond is defined by:

Mod(ψ◦dα) = min(Mod(α),≤ψ)

The AF revision operator ?d based on distance d is defined by:

F ?dϕ=arg(Projatt(fσ(F)◦d(ϕ∧thσ(A))))

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Distances and Minimal Change

Priority to Minimal Change on Acceptance Statuses LetAbe a set of arguments, and N=|A|2+ 1.

dHacc(ω, ω0) =

P

a∈A(ω(acc(a))⊕ω0(acc(a))) +P

a,b∈A(ω(att(a,b))⊕ω0(att(a,b)))

Priority to Minimal Change on the Attack Relation LetAbe a set of arguments, and N=|A|+ 1.

dHatt(ω, ω0) = P

a∈A(ω(acc(a))⊕ω0(acc(a)))

+N×P

a,b∈A(ω(att(a,b))⊕ω0(att(a,b)))

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Distances and Minimal Change

Priority to Minimal Change on Acceptance Statuses LetAbe a set of arguments, and N=|A|2+ 1.

dHacc(ω, ω0) = N×P

a∈A(ω(acc(a))⊕ω0(acc(a))) +P

a,b∈A(ω(att(a,b))⊕ω0(att(a,b)))

Priority to Minimal Change on the Attack Relation LetAbe a set of arguments, and N=|A|+ 1.

dHatt(ω, ω0) = P

a∈A(ω(acc(a))⊕ω0(acc(a)))

+N×P

a,b∈A(ω(att(a,b))⊕ω0(att(a,b)))

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Distances and Minimal Change

Priority to Minimal Change on Acceptance Statuses LetAbe a set of arguments, and N=|A|2+ 1.

dHacc(ω, ω0) = N×P

a∈A(ω(acc(a))⊕ω0(acc(a))) +P

a,b∈A(ω(att(a,b))⊕ω0(att(a,b))) Priority to Minimal Change on the Attack Relation LetAbe a set of arguments, and N=|A|+ 1.

dHatt(ω, ω0) = P

a∈A(ω(acc(a))⊕ω0(acc(a)))

+N×P

a,b∈A(ω(att(a,b))⊕ω0(att(a,b)))

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Example

F1= a b c d Accepted arguments: {a,c} Revision byϕ=acc(a)∧ ¬att(a,b) with priority to minimal change on...

...the attack relation: 1 acceptance status change

I {a}

1 attack change

I removal of (a,b)

F2= a b c d

...acceptance statuses: 0 status change

I {a,c} 2 attack changes

I removal of (a,b)

I addition of (d,b)

F3= a b c d

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Example

F1= a b c d Accepted arguments: {a,c} Revision byϕ=acc(a)∧ ¬att(a,b) with priority to minimal change on...

...the attack relation:

1 acceptance status change

I {a}

1 attack change

I removal of (a,b)

F2= a b c d

...acceptance statuses: 0 status change

I {a,c} 2 attack changes

I removal of (a,b)

I addition of (d,b)

F3 = a b c d

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Example

F1= a b c d Accepted arguments: {a,c} Revision byϕ=acc(a)∧ ¬att(a,b) with priority to minimal change on...

...the attack relation:

1 acceptance status change

I {a}

1 attack change

I removal of (a,b)

F2= a b c d

...acceptance statuses:

0 status change

I {a,c}

2 attack changes

I removal of (a,b)

I addition of (d,b)

F3 = a b c d

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Restriction to Acceptance Formulae

Postulates adapted from the standard belief revision

[Katsuno et Mendelzon 1991]

(AS1) Scσ(F ? ϕ)⊆ S(ϕ)

(AS2) IfScσ(F)∩ S(ϕ)6=∅, then Scσ(F ? ϕ) =Scσ(F)∩ S(ϕ)

(AS3) Ifϕis acc-consistent, then Scσ(F ? ϕ)6=∅ (AS4) Ifϕ≡acc ψ, thenScσ(F ? ϕ) =Scσ(F ? ψ) (AS5) Scσ(F ? ϕ)∩ S(ψ)⊆Scσ(F ?(ϕ∧ψ)) (AS6) IfScσ(F ? ϕ)∩ S(ψ)6=∅, then

Scσ(F ?(ϕ∧ψ))⊆Scσ(F ? ϕ)∩ S(ψ)

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AF Revision based on a Distance

Proposition

Given a pseudo-distanced between sets of arguments, and an AF F,≤dF is the total pre-order between sets of arguments defined by:

ε1dF ε2 iffd(ε1,Scσ(F))≤d(ε2,Scσ(F)).

Givenϕandacc-formula,the revision operator based on the pseudo-distance d ?d which satisfies

Scσ(F ?d ϕ) = min(S(ϕ),≤dF) satisfies(AS1)- (AS6).

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Coming Back to Minimal Change on Arguments Statuses

Proposition

The revision operator with priority to minimal change on the arguments statuses, restricted to acceptance formulae, satisfies postulates(AS1)-(AS6).

Intuition: can be proved by reducing this operator to another one based on a distance between sets of arguments.

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Possible Extensions of the Approach

Open World Revision

GivenF =hA,Ri an AF,B a non-empty set of arguments such thatA∩B=∅,ϕ∈ LA∪B a formula and◦ a KM revision operator, the associatedopen world revision operator?B is defined by:

F ?B ϕ=arg(Projatt(fσ(F)◦(ϕ∧thσ(A∪B))))

Constrained Revision

GivenF =hA,Ri an AF,ϕ, µ∈ LA two formulae and◦a KM revision operator, the associatedµ-constrained revision operator is defined by:

F ?µϕ=arg(Projatt(fσ(F)◦(ϕ∧thσ(A)∧µ)))

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Possible Extensions of the Approach

Open World Revision

GivenF =hA,Ri an AF,B a non-empty set of arguments such thatA∩B=∅,ϕ∈ LA∪B a formula and◦ a KM revision operator, the associatedopen world revision operator?B is defined by:

F ?B ϕ=arg(Projatt(fσ(F)◦(ϕ∧thσ(A∪B)))) Constrained Revision

GivenF =hA,Ri an AF,ϕ, µ∈ LA two formulae and ◦a KM revision operator, the associatedµ-constrained revision operator is defined by:

F ?µϕ=arg(Projatt(fσ(F)◦(ϕ∧thσ(A)∧µ)))

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Summary of this Work

I Revision method for AFs by translation into propositional logic

I Generic method: works for any semantics

I Extended to open world revision and constrained revision

I Use of a rich language:acc(x) and att(x,y)

I Encoding skeptical acceptance for stable and complete semantics

I Definition of a family of revision operators: distance-based revision operators

I Operators adapted to both kind of minimal change: acceptance statuses and attacks

I Characterization of revision operators restricted to theacc case

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Future Work

I Characterization of other semantics and credulous acceptance

I Rationality postulates for other kinds of operators:

I Minimal change on the attack relation

I Formulae on attacks/Unrestricted formulae

I Open world revision, constrained revision

I Implementations of revision operators: SAT solvers

Thank you for your attention!

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Future Work

I Characterization of other semantics and credulous acceptance

I Rationality postulates for other kinds of operators:

I Minimal change on the attack relation

I Formulae on attacks/Unrestricted formulae

I Open world revision, constrained revision

I Implementations of revision operators: SAT solvers Thank you for your attention!

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