This problem is one of the most underestimated problems in enterprise Java applications. The problem is far more complex and labor-intensive than simply reading from and writing to a database, because:

• The database world contains stored procedures, tables, rows, columns, and foreign keys

• The object-oriented Java world contains object references, business rules, complex relationships, and inheritance

• Runtime considerations such as locking, caching, and sequencing must be managed

The problem of bridging these fundamentally different technologies is knows as the object-relational impedance mismatch.