Moreover, your client page may not need to know the user details.
The page could subscribe to a generic item name (for instance: "personal_data"), and the Metadata Adapter would have a chance to rectify the item name, based on user profile information, to a specific name (for instance: "premium_user_data") (see "getItems").

In any case, this requires that your Data Adapter accepts subscriptions for all the possible specific item names, corresponding to different kinds of users. Note that this may imply some redundancy, as some updates may need to be supplied to multiple of these user-kind-related items.