Is it necessary to support bidirectional navigation of an association or should this be dependent on the application requirements? I'm reading Hibernate in action and it is discussed in a way that makes it seem like at the very least a "best practice".

-Mark

You can usually chose if you want an association bidirectional or unidirectional. In some cases, e.g. one-to-one between A and B with a foreign key in B's table, you might have to make it bidirectional if you want to navigate from A to B (that means you also need B to A). Those cases are very rare.