<class name="Customer">
    <set name="Address" batch-size="3">
        ...
    </set>
</class>

- The last visited address.
- The closest address to the customer address.
- The latest (added) address

Address GetLastVisited(Customer c);
Address GetClosest(Customer c);

<bag name="Addresses"  where="CurrentAddressFlag = 1" cascade="save-update" fetch="select" lazy="true">
      <key column="AddressId"/>
      <one-to-many class="Address"/>
</bag>