Identification of messages

The Identification of the messages must use Universally Unique Identifiers (UUID) in its canonical textual representation: 32 hexadecimal (base-16) digits, displayed in 5 groups separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters.

Example: 123e4567-e89b-12d3-a456-426655440000

Note that the only legal characters in an UUID is 0-9 and a-f.

The element OriginalDocumentReference used to refer from one message to another must also contain an UUID.