Why are there multiple data dictionary editions?

DDEX maintains one data dictionary that contains absolutely all the semantics (i.e. meaning) and syntax (i.e. structure) of all terms, defnitions and concepts used in all of the DDEX standards. However, this data dictionary is not published.

Instead, since 2019, DDEX publishes a data dictionary for each standard each of which is effectively an “extract” of the unpublished data dictionary because each standard only uses a subset of all the terms, definitions and concepts set out in the unpublished data dictionary. Each of these data dictionaries is known as a Structural Edition, for example, the ERN 4.3 Edition. Each of these editions contain the structure and terms of all the message(s) specified in each relevant standard. However, these editions do not contain the allowed value sets or the allowed values for those sets. A new version of each Structural Edition for each standard is published every time a new version of the standard is published.

This approach is because if a user wants to know something about a term used in, say, the ERN standard, it would make that user's life more complicated if the user has to look as well, at all terms that are only used in, say, the DSR or RDR standards.

DDEX also publishes an Allowed Value Sets Edition of the data dictionary. This contains all the allowed value sets, the allowed values for each set and their definitions for all of the DDEX standards. This Edition is updated everytime changes are made to an allowed value set.

Finally, in addition, since 2021 DDEX generates a general index, which can be found here. This contains all terms currently used by all the standards since that time. This general index, then points to the various Structural or AVS Editions.