6.2.4 Contractually Mandatory

The messages defined in this standard contain fields with cardinality “0-1” or “0-n”. Therefore these fields are from the standard’s point of view, optional. Such fields may, however, be mandatory when a DDEX message is sent in a specific commercial context.

In such circumstances, a message is deemed conformant only if and when it contains all the “contractually mandatory” fields as agreed by MessageSenderand MessageRecipient.