Value dates for concurrency control and transaction management in interoperable systems

Value dates appear, at present to be the most flexible concurrency control paradigm for autonomous heterogeneous interoperable systems. The protocols are deadlock free, and can be livelock free in the situation when the two-phase locking protocol (2PL) creates a deadlock in practice. Value dates accommodate the autonomy better. The commit protocols possible with value dates can be also more efficient than the two-phase commitment protocol (2PC). The advantages of the value dates make it worth the replacement of 2PL as the standard. Further research should concern the implementation issues. Another important issue is the use of unsafe values. Applications often use unsafe values with value dates for better efficiency, e.g. reservation systems