
<mapping>

        <class name="A">
                <map-to xml="A"/>
                <field name="number"
                       type="integer">
                        <bind-xml name="Number"/>
                </field>
                <field name="item"
                       type="string">
                        <bind-xml name="Item"/>
                </field>
        </class>
        <class name="B" extends="A">
            <map-to xml="B"/>
            <field name="id"
                       type="string">
                        <bind-xml name="Id"/>
            </field>
        </class>

</mapping>