The current top level structure - which is normative! - provides only one entry point (i.e. root element in the schema) into the DATEX II data model, called d2LogicalModel, an instance of the class D2LogicalModel.
First of all, this element / class appear to be named inappropriately. In all other parts of this vast model, class/tag names are chosen to describe their content. The Accident class / accident element tag indicate that inside this class / XML element, the traffic engineering data for an accident is to be found. The only exception is "D2LogicalModel", where the content is far from being such a model, but in reality is a traffic & travel related message!
Furthermore, it doesn seem proper modelling to enforce DATEX data structures - which are enforced to start with d2LogicalModel - to enforce the use of the Exchange package. DATEX payload data should be independent from the exchange mechanis and therefore, there should be a top level element that allows to avoid using Exchange.
The whole Exchange package as such seems badly modelled and should be discarded as long as DATEX specs don't properly deal with it!
Agree, bad nameing of d2LogicalModel
But, the D2LogicalModel is not the payload. The payload is in Payload..
The message that D2LogicalModel carries is Exchange information and Payload..
Maybe we need more then one rootElement?
Or think about services where each service has it’s own pair of request/response elements.
Renaming proposal accepted and will be fixed in v3.0.
Embedding payload in exchange will be looked at in WP 5.4 "exchange".
Fixed in version 3 drafts 2015.