23.4.1. "Typed" one-to-one association

<class name="Person">
    <id name="name"/>
    <one-to-one name="address" 
            cascade="all">
        <formula>name</formula>
        <formula>'HOME'</formula>
    </one-to-one>
    <one-to-one name="mailingAddress" 
            cascade="all">
        <formula>name</formula>
        <formula>'MAILING'</formula>
    </one-to-one>
</class>
<class name="Address" batch-size="2" 
        check="addressType in ('MAILING', 'HOME', 'BUSINESS')">
    <composite-id>
        <key-many-to-one name="person" 
                column="personName"/>
        <key-property name="type" 
                column="addressType"/>
    </composite-id>
    <property name="street" type="text"/>
    <property name="state"/>
    <property name="zip"/>
</class>