Specialising DDEX-Defined Values
As discussed here, DDEX standards allow the communication of user-defined values when none of the DDEX-defined values is suitable in a specific context.
Such user-defined terms are, however, only useful to the recipient of the message if it knows, precisely, what the sender means by this term. There are, however, cases, where it is sensible to signal that a user-defined term is a specialisation of a DDEX-defined term. For example, to indicate that a specific instrument "bell lyre" is a kind of glockenspiel.
This can be communicated as follows:
This enables the recipient to note that the instrument played was not only a bell lyre but also some type of glockenspiel. As a consequence, the recipient can classify the performance by the DDEX-defined value as well as the additional, user-defined value.
The namespace indicates, as usual, the identifty of the company that has created the user-defined term (at least for the communication in this particular message).
Users of the DDEX standards should only use user-defined values when DDEX does not provide any suitable values for their purpose as user-defined values drastically reduce compatibility.
If there is no suitable DDEX-defined value available, users should attempt to specialise a DDEX term (as described here) and only revert to using stand-alone user-defined values as a last resort.
Users of the standards should also contact DDEX to work towards adding any non-confidential user-defined values into future versions of the DDEX standards.