There has been a lot of discussion about how to define and operationalize reputation for on-line communities. Bob Blakley in his beautifully written post – On the Absurdity of Owning One’s Identity – defines reputation as follows:

Your reputation is my story about you. You can’t own this by definition; as soon as you own it, it’s no longer my story about you; it instantly becomes an autobiography instead of a reputation.

James Kobielus has a different take on what reputation is:

Reputation isn’t an attribute of our identity, and it isn’t a story, really. It’s simply an assurance, confidence, or comfort level in which others regard our identity. It’s a vague, qualitative, holistic, often semi-conscious impression, calculated somewhere in the reptilian mind that has descended to us down through the ages. Quoting myself again:
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“Relying parties—-the ultimate policy decision and enforcement points in any interaction—-need many levels of assurance if they’re going to do business with us. They gather assertions and data from many IdM “authorities” (authentication authorities, attribute authorities, etc.) before rendering their evaluations and opening their kimonos. They—-the relying parties—-make reputation evaluations based on information fed in from trusted authorities, from their own experiences with us, from whatever reputation-relevant data they can google across the vast field of received opinion and public record.”
Reputation is a computed halo—positive or negative–around our socially contextualized identities.
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Reputation is a score computed by relying parties in order to determine whether or not to authorize the reputed party to access resources such as jobs, communities, romantic encounters, time of day, etc.
Reputation is an assurance that someone is worth our while.

This is an interesting take although it almost seems like James is defining the process of generating and evaluating trust based on reputation rather then reputation itself. Phil Windley et al in the paper “A Framework for Building Reputation Systems” have a multi-faceted definition of reputation

Reputation is one of the factors upon which trust is based. The is much confusion between trust and reputation. We consider reputation a building block for trust. We are not concerned in this paper with what other factors go into trust, how trust is built, or how trust is exchanged.

Reputation is someone else’s story about me. I can’t control what you say about me although I may be able to affect the factors you based your story on. Every person should be able to have their own story about me.

Reputation is based on identity. Reputation, as someone else’s story, isn’t part of your identity, but is based on an identity or set of identities.

Reputation exists in the context of community. Any given context will have specific factors for what is important in determining reputation. This is different than saying “communities have a reputation about someone.” Communities do not have beliefs, only people have beliefs including beliefs about what others believe.

Reputation is a currency. While you can’t change reputation directly, reputation can be used as a resource. For example, Paul Resnick et. al. has shown the value of a positive eBay reputation [Res00a].

Reputation is narrative. Put another way, reputation varies with time. Reputation is dynamic because the factors that affect it are always changing. Reputation may require weaving together plot lines from different contexts.

Reputation is based on claims (verified or not), transactions, ratings, and endorsements.. How these factors are used in determining reputation is up to each individual. Individuals may use various evidence in making claims or proposing a certain rating or endorsement. The penalty for making false claims or giving false endorsements varies from context to context.

Reputation is multi-level. A reputation isn’t just based on facts, but is also based on other’s beliefs about the target of the reputation. These beliefs are signaled to others in various ways depending on the context.

Multiple people holding the same opinion increases the weight of that opinion. Reputation systems should have some way of weighting scores. As a related issue, repeat behavior is another way of weighting reputation.

Most of these points make a lot of sense…Reputation is really a key ingredient for establishing trust…and trust really is grease to the wheels of commerce and social interactions. Reputation is more then sum total of a person’s transactions on sites like eBay, it is really more of a person’s interactions in various communities.

One of the other characteristics of reputation, which is not captured in any of the definitions, is that reputation can be transferred. E.g. if a high reputation person recommends a particular person, it improves the reputation of the recommended. It’s almost like the recommended person can bask in reflected glory of the high reputation recommender. We should know, as we are in the process of approaching a number of people for help with our startup. In this process, one of the key things we think about is, what is the best way to approach and get introduced to the target, such that we maximize our potential for success. It will be interesting to see on-line reputation systems account for this critical characteristic of reputation.