Trust Metrics
A trust metric is a measure of how a member of a group is trusted by the other members.
Since the definition of trust and reputation, as well as of trust metrics and reputation systems is partially interchangeable, see also our entry on Reputation where we discuss reputation systems.
The Wikipedia article on trust metrics notes that such systems must exhibit "Attack resistance, i.e. the ability to handle agents who participate in bad faith (i.e. who aim to abuse the presumption of trust).
Characteristics
Local vs. Global
"A local trust metric predicts trust scores that are personalized from the point of view of every single user. For example a local trust metric might predict "Alice should trust Carol as 0.9" and "Bob should trust Carol as 0.1", or more formally trust(A,C)=0.9 and trust(B,C)=0.1
On the other hand, a global trust metric computes a single global trust value for every single user.
Local trust metrics start from the assumption that every single trust statement is an equally worthy subjective opinion and that there are no wrong opinions and that there are no global reputation values on which all the users must agree. This characteristics is especially useful when dealing with controversial users which receive very different trust statements from the other users.
Local trust metrics are particularly useful also in order to avoid the tyranny of the majority risk. However they might suffer from a risk on the other side of the personalization scale, daily me or echo chamber, that means that the user loses the point of view of the community at large but just relies on the opinions of few trusted users."
Examples
- eBay's Feedback Rating
- The Slashdot introduced karma system
- The free software Advogato
- The Center for Adventure Economics at Couchsurfing was working on trust metrics, check the CouchSurfing wiki.
More Information
See our entries on Trust and Reputation
Trust Metrics Wiki is a Wiki whose goal is to review, understand, code and compare on same data all the trust metrics proposed so far. TrustLet is a collaborative research effort with comprehensive information on the issue.
External links
Provided by the Wikipedia article at http://en.wikipedia.org/wiki/Trust_metric
- Trust Metrics Evaluation Project of Paolo Massa. The Analyzed Trust Metrics page provides an extensive bibliography of work on the theory and implementation of trust metrics.
- Trustcomp.org is an online community of more than 150 academic and industrial members who research computational trust management and online reputation. There is also a mailing list.
- Raph Levien, 2000. Advogato's trust metric. Electronic manuscript.
- Raph Levien, 2002. Attack Resistant Trust Metric Metadata HOWTO. Electronic manuscript.