Hello Peter,
here is slightly off-topic alternative: perform the necessary validation programmatically using a Tamino Server Extension.
This might not be as clean as a data model based solution, but it is a feasible approach.
A trigger Server Extension can be called when inserting or updating documents, and I think that you could easily code the necessary checks.
Please see the following documentation section for more details on triggers:
C:\Program Files\Software AG\Tamino\Tamino 4.1.1.1\Documentation\servext\setypes.htm#setrig
I hope that helps,
Trevor.
#Tamino#API-Management#webMethods