6.10 Indicating unknown values

When the inclusion of data is mandatory for a particular element in any message but a message sender cannot provide such data, the following values shall be entered:

• In tags of type xs:string: #unknown#;

• In tags of type xs:date: 9999-01-01;

• In tags of type xs:datetime: 9999-01-01T99:01:01; and

• In tags of type xs:duration: PT99H01M01S.

The circumstances under which such behaviour is permissible may be limited in accordance with the bilateral agreement agreed between the message sender and the message recipient.