>>There should be exactly one definition of every filter.

I would agree, but the thing is that hibernate is pretty widely used and it is here for a while, and with such kind of drastic change an effort of maintaining & upgrading legacy applications increases significantly.

Not saying that idea of defining something in ONE class/entity that is applied across ALL entities is not that straightforward, so I don’t see nothing bad if it will be “duplicated”.

The better idea would be probably to move filter definition to some more distinct place like some config xml or any other place that is considered as a singleton per persistence unit, but with the current design I would vote to follow the approach that was there from the very beginning.