The rumour that JPA is based only on Hibernate is a myth that seems to have gotten propagated. I wrote a blog about this once. The persistence API has its roots in ORM products, which includes Hibernate, but also includes other deluxe products like TopLink that have been around for a lot longer (but weren't open source). A common set of ORM features have been adopted and implemented by ORM vendors across the board, with some of the more mature products having extra features beyond the standard set. I won't compare the features in the API to any one particular product, but it suffices to say that each product has its own value-add features that can be used by those that are prepared to go beyond the spec.