Question: In the context of an EVENT DOWNLOAD – IMS Registration (Direction: ME to UICC) as per USIM Application Toolkit specifications, what is the expected content of the IMPU list data object in case of a successful IMS registration with at least one 'active' contact URI?
Option 1: An empty list, indicating no active registrations.
Option 2: A list containing all available IMPUs from the UICC's storage, regardless of their activity status.
Option 3: A list built from URIs of 'aor' attributes with at least one 'active' ME's contact URI within the same registration element, as received in the SIP NOTIFY request.
Option 4: A single default IMPU set by the UICC for all IMS registrations.
Explanation: According to the specifications for EVENT DOWNLOAD – IMS Registration, in the case of a successful registration, the IMPU list should only include IMPUs derived from 'aor' attributes that have at least one 'active' contact URI among the ME's URIs received in the SIP NOTIFY request. This ensures the UICC is updated with the currently active IMPUs for the IMS service.