Properties do not have to derive from subproperties. They can also derive from properties in the same item. For example, suppose a user item descriptor defines a home address and a shipping address. The ship-to address can inherit its value from the home address, like this:

<item-descriptor name="user">
    <property name="shipToAddress" writable="false" item-type="address">
    <table name="user" >
      <property name="shippingAddress" item-type="address">
      <property name="homeAddress" item-type="address">
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