I defined reputation in a recent post. More specifically, I said that reputation isn't identity. Dick Hardt disagrees. To tell the truth, I hadn't remembered that slide from his famous identity presentation.

Dick refers to a definition of reputation from dictionary.com

reputation:
3. A specific characteristic or trait ascribed to a person or thing

and says

To me, this makes it clear that reputation is part of your identity. Phil states that identity data is not transaction data or reputation data. I think it is. An example of transaction data being identity: "I'm the guy that bought that black sweater yesterday."

Reputation is a bit trickier to understand as there are a few meanings to the word. Using the definition above, it is clear (to me :-) that a characteristic ascribed to a person is reputation. Dick is tall. Dick is male. I take a broad view of what I mean by reputation. It is what any third party says about me. I see this as identity, since this is how that third party is identifying me. It may also be useful to other parties, if they trust that third party. If it is useful to other people, then it is valuable for me to be able to move that identity data around.

From Identity 2.0 » Identity=Reputation
Referenced Fri Feb 10 2006 15:26:01 GMT-0700 (MST)

The definition that Dick uses isn't the only one. The other two are:

reputation:
1. The general estimation in which a person is held by the public.
2. The state or situation of being held in high esteem.

I think most people would agree that these more closely match what they think of when they hear "reputation" than any attribute. When someone loses 25 pounds, we don't think "what a blow to their reputation!"

The problem with defining identity broadly (identity == reputation, identity == transactions, etc.) is that we lose the ability to do anything useful with it. In particular, teasing out the privacy concerns gets much harder.

Take the fact that Dick bought a sweater. Certainly his participation in that transaction can be used to identify him. I'm not arguing that. But to say that it's part of his identity is overly broad. There are at least two parties to the transaction and they both have a stake in it.

Reputation is even more problematic. Reputation, in definitions 1 and 2 at least, is what others say about you. Scott Lemon maintains that our identity is made up of only things that others assert about us. Again, this goes too far. To include everything that anyone says about you in your identity is to create a big hairball that's impossible to untangle.

I'm not trying to start a semantic war here. In common usage, these concepts are frequently comingled. Nevertheless, I believe that separating identity, transactional data, and reputation serves us better than combining them does. We gain more intellectual leverage in architecture and design problems when we think of identity in a narrow sense, transactional data being jointly owned, and reputation being calculated from those, and other, factors.