Data integrity for concurrent engineering transactions

Whenever concurrent engineering applications share and modify common data, global data integrity across the boundaries of a single application is a key requirement of concurrent engineering applications. On the other hand, data integrity cannot be achieved without the presence of transaction synchronization across the boundaries of database systems. The challenge is to guarantee that global transactions leave these multiple databases in a globally consistent state and to avoid that global integrity checks unnecessarily block other application transactions. We present an improved approach to synchronization that offers both, unlimited concurrency between global integrity constraint checks and local transactions, and increased concurrency of global integrity checks and global application transactions, thereby contributing to a higher performance of global integrity checks. The key idea behind our approach involves the classification of integrity constraints according to their requirements for synchronization. We show that depending on the integrity constraint formulas, some integrity checks have to be synchronized with write operations of concurrent transactions, whereas other integrity checks need no synchronization at all, i.e. they may be concurrently performed to arbitrary write operations of other transactions. This is the reason why we suggest that conflicts between integrity constraint checks and write operations are synchronized using a different method to that of conflicts between queries and write operations and why we suggest the use of an adaptive synchronization strategy for integrity checks. Our strategy provides for a certain class of integrity constraints that the integrity constraint itself is locked instead of the database objects, in order to achieve both goals, i.e., to guarantee global consistency of data while increasing the concurrency of global integrity checks. Since our approach blocks significantly fewer resources for global integrity checking than the conventional approach, we consider it to be an important contribution towards the enforcement of global cross-database integrity for concurrent engineering applications. Finally, we extend our results to triggers and coordination rules in peer-to-peer systems for concurrent engineering.