When you open up a UPDM Exchange Element, and go to the field called "Defined By" you can enter in the Entity Items that define that Exchange Element. When you do this, it automatically generates the "Details" relationship from the Entity Item to the Exchange Element.
However, it does not work the other way around. When you create the "Details" relationship from an Entity Item to an Exchange Element, it does not populate the "Defined By" field.
This doesn't seem like much of a big issue, but it is somewhat cumbersome because in order to populate the Defined By field, you have to use the pop-up window and select/multi-select based on the containment tree, vice multi-selecting on the diagram, which is much easier.
Is there a reason why this works only in one direction? I wonder if NoMagic could consider changing this feature to allow that, but it could be that it's quite a trivial problem.