gistfile1.xml

<?xml version="1.0" encoding="utf-8"?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" 
                   default-lazy="false" 
                   assembly="NHibernate.Core.Entites" 
                   namespace="NHibernate.Entites" 
                   default-access="field.camelcase-underscore">
  <!-- Customer is located in assembly NHibernate.Core.Entities -->
  <class name="Customer" table="Customers" xmlns="urn:nhibernate-mapping-2.2">
    <id name="Id" column="Id" type="Int64">
      <generator class="native" />
    </id>
    <component name="Name" insert="true" update="true">
      <property name="LastName" column="LastName" length="255" type="String" not-null="true">
        <column name="LastName" />
      </property>
      <property name="FirstName" column="FirstName" length="255" type="String" not-null="true">
        <column name="FirstName" />
      </property>
    </component>
    <!-- xCustomer is located in assembly NHibernate.XTend.Washinton.Entities -->
    <joined-subclass name="xCustomer" table="xCustomer">
      <key column="CustomerId" />
      <property name="CustomerType" column="CustomerType" length="255" type="String" not-null="true">
        <column name="CustomerType" />
      </property>
    </joined-subclass>
  </class>
</hibernate-mapping>