3, Trust in Multi-Agent Systems

Notes taken from 'Trust in Multi-Agent Systems' (2004), by Sarvapali D. Ramchurn et al.

1, Introduction
Trust - a belief that the other party will do what it says it will (being honest and reliable) or reciprocate (being reciprocative for the common good of both), given an oppurtunity to defect to get higher payoffs.
Individual-Level Trust - whereby an agent has some beliefs about the honesty or reciprocative nature of its interaction partners.
System-Level Trust - whereby the actors in the system are forced to be trustworthy by the rules of encounter (i.e. protocols and mechanisms) that regulate the system.

2, Individual-Level Trust
Trust-Models at the Individual Level - classified as either learning (and evolution) based, reputation based, or socio-cognitive based.
Learning and Evolving Trust - an emergent property of direct interactions between self-interested agents. We assume that agents will interact many times rather than through one-shot interactions.
Reputation Models - the opinion or view of someone about something, mainly derived from an aggregation of opinion of members of the community about one of them.
Socio-Cognitive Models of Trust - forming beliefs according to the assessment of the environment and the opponent's characteristics which could also include an analysis of past interactions.

3, System-Level Trust
Open Multi-Agent Systems - agents interact via a number of mechanisms or protocols that dictate the rules of encounter, e.g., auctions, voting, contract-nets, bargaining, market mechanisms etc.
System-Level Trust - subdivided in terms of:
i, devising truth-eliciting interaction protocols.
ii, developing reputation mechanisms that foster trustworthy behaviour.
iii, developing security mechanisms that ensure new entrants can be trusted.

4, Discussion and Conclusion
A classification of approaches to trust in multi-agent systems:

Individual-Level (Socio-cognitive/Reputation/Evolutionary-and-Learning models) -> Reasoning -> TRUST <- Actions <- System-Level (Trustworthy-Interaction/Reputation/Distributed-Security mechanisms)