Thou shalt remember thy data
This requirement is evident from a database point of view, but a novelty from a programming language point of view, [Atkinson et al. 83]. Persistence is the ability of the programmer to have her/his data survive the execution of a process, in order to eventually reuse it in another process. Persistence should be orthogonal, i.e., each object, independent of its type, is allowed to become persistent as such (i.e., without explicit translation). It should also be implicit: the user should not have to explicitly move or copy data to make it persistent.