Thou shalt accept concurrent users
With respect to the management of multiple users concurrently interacting with the system, the system should offer the same level of service as current database systems provide. It should therefore insure harmonious coexistence among users working simultaneously on the database. The system should therefore support the standard notion of atomicity of a sequence of operations and of controlled sharing. Serializability of operations should at least be offered, although less strict alternatives may be offerered.