If the participant is a person, then the User ID shall be the identifier used for that person on this particular system, in the form of loginName@domain-name.
If the participant is an identifiable process, the UserID selected shall be one of the identifiers used in the internal system logs. For example, the User ID may be the process ID as used within the local operating system in the local system logs. If the participant is a node, then User ID may be the node name assigned by the system administrator. Other participants such as threads, relocatable processes, web service end-points, web server dispatchable threads, etc. will have an appropriate identifier. The implementation shall document in the conformance statement the identifiers used, see A.6. The purpose of this requirement is to allow matching of the audit log identifiers with internal system logs on the reporting systems. .
When importing or exporting data, e.g. by means of media, the UserID field is used both to identify people and to identify the media itself. When the Role ID Code is EV(110154, DCM, “Destination Media”) or EV(110155, DCM, “Source Media”), the UserID may be:
a URI (the preferred form) identifying the source or destination,
an email address of the form “mailto:user@address”
a description of the media type (e.g. DVD) together with a description of its identifying label, as a free text field,
a description of the media type (e.g. paper, film) together with a description of the location of the media creator (i.e., the printer).
The UserID field for Media needs to be highly flexible given the large variety of media and transports that might be used.