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“Do not trust people - they are capable of greatness”
Stanislaw Lem
Trust ModelsSteve Marsh
Carleton University, November 2nd [email protected]
© stephen marsh, 2009QuickTime™ and a
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Outline
Why
What
How
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Trust as Syllogism
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Yes, but why in agents?
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Societies and decisions
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No wait!
What…
… isn’t it?
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Trust is complexity reduction
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Trust is reasoning
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Trust is observability
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Trust is not control
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Trust is risk in action
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Trust is seen in action
Or the air
Like light
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Don’t just talk about it, do it…And see it…
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What… On Trust Models
Types
Functions
Representations
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Hybrid (possibly)
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Modes
(so, what’s it for?How’s it work?)
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Establishment
Reasoning
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Establishment
Reasoning
Action
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Fuzzy Terms
Logic
Real Numbers
Integers
Vectors
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How…Two ‘real life’ models
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Marsh; 1994, 2009Castelfranchi (et al); (various), 2009
(there are lots more…)
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Types of Trust
The Marsh Model
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Types of Trust 1:Basic
€
Tx
The Marsh Model
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Types of Trust 2:General
€
Tx (y)
The Marsh Model
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Types of Trust 3:Situational
€
Tx (y,α )
The Marsh Model
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How much do I have?
€
Tx (y,α ) = Ux (α ) × Ix (α ) ×) T x (y)
The Marsh Model
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How much do I need?
€
C _ Tx (y) =Riskx (α )
Competencex (y,α ) +) T x (y)
× Ix (α )
The Marsh Model
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Do I ‘Trust’ Thee?
€
Tx (y,α ) ≥ C _ Tx(y,α ) → Trustsx (y,α )
The Marsh Model
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Distrust, Mistrust, Untrust, Ambivalence
Oh My!
The Marsh Model
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Regret
€
Regret x (α ) = (Ux (α ) −Ux (α −)) • f (κ ,λ ,μ)
The Marsh Model
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Regret Adapts Trust (with Understanding)
€
f =C _ Tx (α )t + Tx (y,α )t
Ξx
× (Regret x (α ) − Regret y (α ))
The Marsh Model
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Anticipatory Regret
€
C _Tx (y) =Riskx (α )
Competencex (y,α ) +) T x (y)
× (Ix (α ) − ARx (α −))
The Marsh Model
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Forgiveness Repairs Trust
€
Tx (y)t +tFtx = Tx (y)t +tFtx−1 + Fkx
The Marsh Model
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Forgiveness Function
€
Fkx =(Regret y (α ) − Regret x (α ) + Ix (xy))
Ftx
× Tx (y)
(There are limits to Forgiveness)The Marsh Model
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Continuum
-1 10Distrust Trust
UntrustC_TLimit of
Forgivability
The Marsh Model
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A Logical Model
The Castelfranchi et al. Model
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Core Trust and(Generalized) core trust
The Castelfranchi et al. Model
€
CoreTrust (i, j,α ,ϕ ) = GoaliXϕ ∧Plausi(Afterj:αϕ ∧Int j (α )∧I Pre( j,α )∧E Pre( j,α ))
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Distrust and(Generalized) distrust
The Castelfranchi et al. Model
€
Distrust(i, j,α ,ϕ ) = Goali Xϕ ∧Plausi(¬ Afterj:αϕ ∨¬ Int j (α )∨¬ I Pr e( j,α )∨¬ E Pr e( j,α ))
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Mistrust and(Generalized) mistrust
The Castelfranchi et al. Model
€
Mistrust(i, j,α ,ϕ ) = Goali Xϕ ∧Plausi (Afterj:α¬ ϕ ∧Int j (α )∧I Pr e( j,α )∧E Pr e( j,α ))
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Delegation (reliance)
The Castelfranchi et al. Model
€
Delegate(i, j,α ,ϕ ) = GoaliDoes j:αϕ
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Decision to trust
The Castelfranchi et al. Model
€
DecideTrust (i, j,α ,ϕ ) = CoreTrust (i, j,α ,ϕ )∧Delegate(i, j,α ,ϕ )
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Comparative Trust
The Castelfranchi et al. Model
€
(z,β,ϕ ) <iTrust ( j,α ,ϕ ) =
Goali Xϕ ∧
((Afterz:βϕ ∧Intzβ∧I Pr e(z,β )∧E Pr e(z,β )) <i
((Afterj:αϕ ∧Int jα ∧I Pr e( j,α )∧E Pr e( j,α ))
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Expressiveness and non-reductionismvs
Implementability
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Where does it all fit?
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Where to look for information
Start here… And here…
Try a google search…
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“Never trust a man who, when left alone in a room with a tea
cosy, doesn’t try it on”
Billy Connelly