11.1 Introduction

Although the concept of a user profile is well understood and well used on the Internet today, we start from a different assumption each user already has many profiles held by the service providers with whom the user has been interacting. The overall user profile (called from here on the 'distributed user profile'), therefore, is the set of all of these distributed profiles.

The problem with the distributed user profile is that it may not be easy to use. For example, consider the situation where one user has two different profiles with two different providers (held in two different databases) with no link between the two profiles. If privacy was not a concern, and if the user has used the same identity with both providers, then, in principle, the two profiles could be consolidated, but, in the real world, two separate organisations will be obliged by privacy protection acts not to disclose user information. Two possible exceptions to the above arguments would be in cases where:

• one organisation merges or buys another;

• explicit permission is asked from each user as to what information can be shared with which other organisations.

An example of the former would be the purchase of Abacus by DoubleClick [1], which spurred a lot of privacy controversy, and an example of the latter would be Microsoft's Passport service [2], where users are asked what information can be shared with sites participating in Passport.

In general, however, it is...