* Take a look at the attached diagrams
* First create the upper diagram
* Then select the containment relationship and choose the other as its EOpposite.
* You obtain the lower diagram, with validation marks on the connection "The opposite of the opposite may not be a reference different from this one".
* The original connector to "myOwner" does not disappear, but the other one becomes multi-edged anyway. If you delete the original myOwner connection, also the myOwner edge of the multi-edged one disappears. This demonstrates that they are linked as one would expect.
I know that the manual prescribes the use of the palette item "bi-directional reference". The fact that you can also choose an EOpposite on a normal Composition would trigger one to expect that you can evolve a normal Composition into one having an EOpposite.
Can this strange behaviour be avoided?
* Eclipse Luna
* Ecore Diagram Editor 188.8.131.52409150953 (same behaviour in nightly)
Oops, I clearly missed something
I missed the step to set the EOpposite of the second connector as well.
Although the validation message is technically correct, it didn't lead me to realizing the issue.
Maybe consider rephrasing?