class Address
   {
      public string Name { get; set; }
      public virtual ISet Contacts { get; set; }
      
      public Address()
      {}
   }

   class Contact
   {
      public Address Address { get; set; }
      public string Name { get; set; }

      public override bool Equals(object obj)
      {...}
      public override int GetHashCode()
      {...}
   }

namespace NewNHibernate
{
   class Contact
   {
      public String Id { get; set; }
      public Address Address { get; set; }
      public string Name1 { get; set; }
      public string Name2 { get; set; }
      public string Name3 { get; set; }

      public Contact() { }
      public Contact(Address address)
      {
         Id = "NameOfContact";
         Address = address;
      }
   }
}

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" auto-import="false" default-lazy="false">
  <class name="NewNHibernate.Contact, NewNHibernate">

    <id name="Id" type="string" >
      <generator class="assigned"/>
    </id>

    <property name="Name1" />
    <property name="Name2" />
    <property name="Name3" />

    <many-to-one name="Address" class="NewNHibernate.Address" />

  </class>
</hibernate-mapping>

namespace NewNHibernate
{
   class Address
   {
      public string Name { get; set; }
      public string Name2 { get; set; }
      private ISet contacts = new HashedSet();

      public ISet Contacts
      {
         get { return contacts; }
         set { contacts = value; }
      }
   }
}

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" auto-import="false" default-lazy="false">
  <class name="NewNHibernate.Address, NewNHibernate">

    <id name="Name" type="string">
      <generator class="assigned"/>
    </id>
    <property name="Name2" />

    <set name="Contacts" inverse="true" cascade="all-delete-orphan">
      <key column="Address" />
      <one-to-many class="NewNHibernate.Contact, NewNHibernate" />
    </set>

  </class>
</hibernate-mapping>