A computer system is presented for facilitating storage and retrieval of user attribute information within a federated environment at entities that manage such information as a service. Through enrollment processes, certain domains inform online service providers of identities of attribute information providers that may be used to retrieve user attribute information for a particular user. When performing a user-specific operation with respect to a requested resource, e.g., for personalizing documents using user attribute information or for determining user access privileges for the resource, an e-commerce service provider requires user attribute information, which is retrieved from an attribute information provider that has been previously specified through an enrollment operation. The e-commerce service provider may store the identity of the user's attribute information providers in a persistent token, e.g., an HTTP cookie, that is available when the user sends a request for access to a resource.