I m 试图绘制类似于流体原的地图:

<class name="IAccountManager" 
    abstract="true" 
    table="IAccountManager">

    <id name="Id">
            <generator class="hilo"/>
    </id>

    <union-subclass
            table="DefaultAccountManager"
            name="DefaultAccountManager">
            <property name="FirstName"/>
    </union-subclass>

    ... more subclasses
</class>

如何做到这一点?