The type of the primary key (long, String, etc) is intimately related to the
choice of generator class. For instance the default 'native' generator class
typically requires the primary key property to be of type 'long' and to use
an 'int' with 'uuid.hex' is not meaningful.
On the list Chad Brandon suggested that this should be solved using an OCL
I have found this to be a problem in recent versions of RC1 when but all
versions in the 3.0 train probably has this 'problem'.