Yes, it certainly is and IMHO the whole treat operator is grossly underspecified in JPA. The spec only expends a few lines on this operator, while it is very complex to get right and has many kinds of complex interactions with other constructs. It’s good to see you are working on this (and it seems one of my other tickets as well). Once this is merged, I’ll see if I can find some time to test a snapshot build with our product.