If the participant is a person, then AlternativeUserID shall be the identifier used for that person within an enterprise for authentication purposes, for example, a Kerberos Username (user@realm). If the participant is a DICOM application, then AlternativeUserID shall be one or more of the AE Titles that participated in the event. Multiple AE titles shall be encoded as:

AETITLES= aetitle1;aetitle2;…

When importing or exporting data, e.g., by means of media, the AlternativeUserID field is used either to identify people or to identify the media itself. When the RoleIDCode is (110154, DCM, "Destination Media") or (110155, DCM, "Source Media"), the AlternativeUserID may be any machine readable identifications on the media, such as media serial number, volume label, or DICOMDIR File-set ID (0004,1130).