Contract for classes (specifically, entities and components/embeddables) that are "managed". Developers can choose to either have their classes manually implement these interfaces or Hibernate can enhance their classes to implement these interfaces via built-time or run-time enhancement.

The term managed here is used to describe both:

• the fact that they are known to the persistence provider (this is defined by the interface itself)
• its association with Session/EntityManager (this is defined by the state exposed through the interface)