Exception is thrown, if an object is about to be saved in a transaction,
but the same object (or another representation of the same data) is under
modification in another thread.
All objects implementing this interface are considered "dynamic", which
means they can define their own attributes,attribute types and the
table their "class" dynamically.
Note however, that when you change the set of attributes for this kind of
objects, their representation in the database will change.