Some user have complained about the monolitic, large DATEX II schema. They suggest to consider a more modular approach, where the schema is split into different schemas that import/inlcude each other in a suitable way. Whether this applies just for the distribution of the schema of various files or whether this implies splitting up into several namespaces is to be considered. The impact on sub-schema generation will also have to be looked at.
The schema is only a generated artefact in DATEX II. This proposal does not add clarity on the modelling level (UML), but makes maintenance of the model and the mapping more complex.