Why can't you put the inverse="true" on the many-to-one side of a bidirectional association of a collection.

ex:
in class Y:
<many-to-one name="x" column="xKey" class="X" />

in class X:
<bag name="ys" cascade="all-delete-orphan" inverse="true" >
<key column="xKey"/>
<one-to-many class="Y"/>
</bag>

Why couldn't you put the inverse="true" in the many-to-one like so:
<many-to-one name="x" column="xKey" class="X" inverse="true" />

So that the saves would happen through the collection? Right now,the collection does not get persisted when saving X.

The cascade attribute provides the saving/update etc mode for the collection.
Read about the various option (try 'all') at
http://www.hibernate.org/hib_docs/reference/en/html/collections.html

Shouldn't all-delete-orphan work?