NHibernate - <natural-id/>

A natural id is a way to refer to a unique field of an object as a substitute of the real entity identifier. A good (and typical) example of that would be with the User entity. We have the user name and the user id, both are unique, but the user id is usually something that is generated by our application and has no relation to the a human being. In other words, user #123814 doesn’t mean anything to me, while user ‘ayende’ has a meaning to us.