Most standard identifiers communicated in DDEX messages have a well-documented syntax. ISRCs, for example, are made up of two characters (the country code), followed by three alphanumeric characters (the registrant code), two digits (the year of reference) and, finally, five digits (the designation code); ISWCs are made up of the letter “T” followed by nine digits (the work identifier) and one character (the checksum calculated in accordance with a standard-specific algorithm).

A DDEX message can be deemed to be invalid if it contains a string in a field for a specific standard identifier that does not follow the published syntax of that identifier. The same applies to cases where the check character is wrong. 

Consequently, a recipient of such a DDEX message would be at liberty to reject such a message and inform the message sender about the reason for the rejection.

Note: many identifiers, including ISRCs and ISWCs are written, when presented for human consumption, with dashes and/or dots between the individual elements to improve readability (e.g. JM-K40-14-00212 or T-034.524.680-C). These dashes and/or dots are not part of the official syntax and must therefore not be used in DDEX message tags.

Thus, communicating, say, an ISRC with dashes in a DDEX message would violate the identifier’s syntax – and thus the DDEX message format. Such a message could be rejected by the message recipient.