An IPersistable object of a PersistStore persists as a serial element in a Log Stuctured Store (LSS).
A serial element in the LSS is uniquely identified by a 64 bit Seid. Therefore
in a given PersistStore an IPersistable object is uniquely identified by its Seid.
The Seid is also called an Object Identifier (OID).
In other words an OID uniquely identifies an IPersistable object in a PersistStore.