All components for data types are derived from the superclass "DataValue". But the component "DataValue" can't be found in the tree (of the DATEX-Tool), as there's nowhere a direct access to this class. Newertheless it's generated properly in the .xsd; but the idea is to deselect some of the optional attributes in it, which is not possible in my opinion (there might be even some more situations like this).
Yes, you are correct. DataValue is a special case, here the link(associations) is to the concrete siblings. Other places the associations are to the base class. I have found no other place in the model then this. The question is how this should be represented in the Tree..
Other difference with the DataValue class is that some attributes are XML attributes, but that should make no diference.
Fixed in version 2.1