Enterprise Java Community: Java and the Empowered Database: "February 2006
Introducing R/O Mapping - A concept to have more business logic in the database and reduce the amount of Java code that deals with database issues
The connection between object-oriented systems and relational databases is commonly solved by employing a so-called O/R mapping (ORM) framework whose goal it is to map object-oriented models to entity relationship models which are used, often generated, in relational databases. The bridging between two entirely different modelling techniques results in a so-called impedance mismatch, that needs to be overcome."
The Pro's and Cons section is especially interesting.