Extended transaction processing based on dependency rules

Various extensions of the classic ACID transaction model have been discussed to eliminate its restrictions. To cover the requirements of different kinds of complex and long-lived applications, the ConTract model allows several extended transaction models to be used concurrently as needed. As a prerequisite, an integrated mechanism to control their execution is required. Dependency rules (DR) defining constraints on transactional state transitions have been discussed recently to specify extended transaction models. The author shows how DRs can be used to control the execution of the steps an extended transaction consists of. A major issue is to ensure that all transactions can be committed or aborted some time (liveness) in compliance with the DRs( safety). The solution is based on temporal logic to build a dependency graph (DG) from the DRs. Liveness and Safety are now defined in terms of a consistent DG and appropriate algorithms are presented preserve the DG's consistency. >