Creating hibernate inheritance mappings using joined-subclass<newbie>

In my database I have a parent table that has 3 child tables.  The pk's of 
the child tables have an fk relationship to the pk of the parent table. 
According to Hibernate this is the appropriate method for setting up and 
inheritance relationship between tables.  The Hibernate mapping to 
represent this relationship uses the <joined-subclass> tag under the 
<class> tag of the parent class.  I have been trying to figure out how to 
generate the joined-subclass mapping using middlegen without luck, can 
someone point me in the right direction?

Hibernate 2.1.7
Middlegen 2.1.2



Louis M. Burroughs III