In addition to deciding which attributes he discloses to which service provider (and under which conditions), the user will also have the opportunity to choose which digital identity (identity provider or other authoritative source for attribute information) he uses to provide these attributes.
In this regard the TAS3 approach is somewhat similar to the Microsoft Cardspace model; however, the TAS3 approach is more advanced for two main reasons. First, the user has the ability to become actively involved in the management of the identifiers/ pseudonyms associated with his respective digital identities, and the correlations between them. Second, the TAS3 approach provides for an important functionality currently not provided by Cardspace, namely the ability to aggregate attributes across different partial identities to respond to a single request from a service provider, without compromising the privacy of the data subject with regards to the identifiers associated with these different partial identities.
Another advantage provided by TAS3 is the governance framework. The contract framework, coupled with the required polices, creates an ecosystem-wide binding of obligations. Most systems can only bind a limited number parties to a transaction and then only for a limited number of transactions.
See deliverables D2.1 (high-level), D4.2 D7.1 and upcoming deliverables of WP6 [SEW11].