Download On how agents make friends: mechanisms for Trust Acquisition

On how agents make friends:
mechanisms for Trust Acquisition
Babak Esfandiari & Sanjay Chandrasekharan
Carleton University
May 29th 2000
Workshop on Trust, Deception and
Fraud
Motivation
• Theoretical:
– most current work on Trust is descriptive and
non-constructive
– lack of emphasis on dynamic aspects of Trust
such as Trust Acquisition and update
• Practical:
– trust acquisition can accelerate multi-agent
learning, and cooperation in general
– application in e-commerce, network
management, RoboCup
May 29th 2000
Workshop on Trust, Deception and
Fraud
Definitions
• Trust is a relation between two agents:
T: A x A -> [0,1]
ex: T(jules, jim) = 0.8
trusts jim 80%
jules
• Trust Acquisition is the process or
mechanism that allows the calculation and
update of T.
May 29th 2000
Workshop on Trust, Deception and
Fraud
Trust Acquisition by Observation
• Bayesian model:
T(John, Mary) = P(M=T|S)
Scoring situation
S
S
P(J=T) P(J=F)
John Scores
P(M=T) P(M=F)
Mary Scores
T
60
40
T
70
30
F
10
90
F
10
90
May 29th 2000
Workshop on Trust, Deception and
Fraud
Trust Acquisition by Interaction
• Exploratory protocol
• Query protocol
[Maes]
Wendy
Lisa
ask()
reply()
evaluate()
 Trust(wendy,
May 29th 2000
lisa)= wendy.evaluate(lisa, replies)
Workshop on Trust, Deception and
Fraud
Institutionalizing Trust
• Institutions as a Brooksian way to reduce
cognitive load
 Trust(bill, institution) = 1
• Learning prejudice (!) through induction
May 29th 2000
Workshop on Trust, Deception and
Fraud
Trust Propagation
(les amis de nos amis sont nos amis)
• Social Network Analysis perspective
• Trust(A,C) =? Trust(A,B) x Trust(B,C)
C
• multiple paths
• cycles
D
B
• task-specific trust
 [min_trust,
max_trust]
A
(of all paths with no cycle)
E
 possible coloring of the edges
May 29th 2000
Workshop on Trust, Deception and
Fraud
Conclusion
• List of trust acquisition mechanisms
• Next: application to RoboCup, e-commerce
and network management
May 29th 2000
Workshop on Trust, Deception and
Fraud