5.3. Mapping a class more than once

It is possible to provide more than one mapping for a particular persistent class. In this case you must specify an entity name do disambiguate between instances of the two mapped entities. (By default, the entity name is the same as the class name.) Hibernate lets you specify the entity name when working with persistent objects, when writing queries, or when mapping associations to the named entity.
<class name="Contract" table="Contracts" 
    <set name="history" inverse="true" 
            order-by="effectiveEndDate desc">
        <key column="currentContractId"/>
        <one-to-many entity-name="HistoricalContract"/>

<class name="Contract" table="ContractHistory" 
    <many-to-one name="currentContract" 
Notice how associations are now specified using entity-name instead of class.