Conditional transactions: a model of computation for active databases

A transaction model for active databases is introduced. Concurrent execution of rules needs to be carefully managed to ensure consistent semantics. It is shown that serializability is not always sufficient for correctness. A new criterion, conditional conflict serializability (CCS) is developed and shown to ensure the desired correctness. A graph-based scheduler for it is presented. Practical schedulers should also be recoverable, which the graph-based scheduler is not. The authors prove that conventional two-phase locking also achieves CCS, and can thus be used in practice