<class name="A" table="A">
   
    <id name="id" column="ep_id" type="integer" unsaved-value="null">
      <generator class="increment" />
    </id>     
    <property name="typ" column="ep_typ" type="string" length="10" />
    <property name="data" column="ep_data" type="date" not-null="true" />
     
    <joined-subclass name="AB" table="AB">
      <key column="cza_id" />
      <property name="x" column="cza_x" type="integer" not-null="true" />
    </joined-subclass>

    <joined-subclass name="AC" table="AC">
      <key column="czz_id" />     
      <one-to-one name="classAB"
         class="AB" foreign-key="cza_id"/>
    </joined-subclass>

</class>