Some kinds of reputation

I've argued that reputation is an inherently subjective assessment of a set of assertions associated with a persona (I need a less-jawbreaking way to say that). That doesn't mean that there's no point in trying to model it, just that there's no single or objective model.

On the other hand, there are any number of real-world examples of reputations, some of which already have well-known models. Some that come to mind:

eBay: Michael O'Connor Clarke talks about this in his piece on personal reputation management. In eBay, your reputation is a summary of the positive and negative feedback you've received over the course of your transactions. There are various checks and balances that make the system work (e.g., if you bash someone needlessly, it will catch up to you).

Clarke states that "It's your reputation, but you don't even own it. If you ever chose to leave eBay, you can't take it with you."

I'd basically agree but I might put it differently. Your eBay reputation is a summary of the history of your eBay persona. If you can convince someone that, say, your Blogger persona and your eBay persona are both you, then you've convinced them that, say, the person who posted "I just bought a new camera on eBay" has a 98% positive rating on eBay. If you leave eBay, you lose a means of convincing someone that you made those particular transactions and got those particular feedback votes.

If you can carry those assertions with you, you can carry your reputation with you. For example, a subculture of eBay users could all agree to send appropriately signed records of their transactions and feedback to a trusted third party as they make them. This slice of your eBay reputation would then be portable (assuming eBay doesn't take this sort of thing amiss).

Blogrolls and social networking sites: Clarke mentions these as well. Blogrolls are just a less formal version of the same basic idea. Again, the problem in carrying over reputations from one service to the next is mostly a matter of linking up the personae.

I could imagine a sort of "meta-network" service where I can tell the meta-service that I've joined a new service, giving it my login, password etc. The meta-service can then look up who else it knows that has already joined that service and who is connected to me in other services I belong to and, subject to rules I specify, invite them on my behalf.

Similarly, it can accept invitations on my behalf from people it knows I've accepted invitations from in other services. It can monitor my various services and propagate changes across them. E.g., if I blogroll someone on Blogger, it could automatically invite the other person on LinkedIn, and if they also subscribe, accept the invitation on their behalf.

This seems somewhat different from OpenID, in that the service stores connections as well as identities, and from FOAF, which appears more concerned with marking up existing pages to make them more easily machine-readable. As always, though, I may be slow on the uptake here.

The various public-key webs of trust: This is probably what I was thinking about here, when I said "It occurs to me that there is a different, more Web 2.0-ish notion of reputation as a network of people's ratings, other people's ratings of their ratings, and so forth." Each key is a persona, and the trust scheme of the system you're using accumulates the various assertions known about a persona into an assessment of the persona -- its reputation, in other words.

Poker: This is a world where you literally buy and sell your reputation. Each bet you make says something about how you play. Do you bluff a lot? Are you likely to call someone else's bluff? Do you play every hand or do you fold all but the best? Every time you act, you provide information for the other players' answers to those questions, and that in turn affects how they will play against you and thus affects your winning chances.

Are there other poker-like situations on the web, outside gaming? I'm sure there must be, but they're not coming to mind at the moment.

Recommendation lists on e-commerce sites: These aren't so much reputations in the usual sense of trustworthiness, but they are assessments of assertions about a persona. The user ID is the persona and the assertions record the purchasing history and other actions of that user. The site then uses its own secret sauce to cook these up, often together with the histories of other users, into a list of recommendations.