This article is from the FAQ, by with numerous contributions by others.
The Mjolner System contains a library that implements a persistent store for
BETA objects. Any BETA object can be stored into the persistent store and
subsequent obtained from the store in a type-safe way. There are no
requirements that the persistent objects must inherit from any specific
superpattern, and persistent objects are fully type-checked both when saved
in the persistent store, and when retrieved from the persistent store.