Main advantage with Hibernate annotations is the fact that a simple POJO (also called a Business Object the most of time) can become persistent through Hibernate annotations (or actually JPA) .

In the scenario where our conceptual domain model (business objects used by clients) does not exactly reflect the physical model (database), how to deal with? Should I create a "second" model that represents the "true" business objects used by clients AND a "data storage object" containing mapping Hibernate annotations? Of course, with this solution, DAOs will be responsible to convert each BO to Data Object and vice-versa.