Emulating Cooperative Transactions upon Standard Database Systems

Complex database applications like CAD/CAM or CASE introduce the need for long duration and/or cooperative transactions. Unfortunately, commercial DBMSs generally support a flat transaction model without cooperation. While many studies have been conducted on the management of more powerful transaction models on top of existing DBMSs (e.g., workflow management), few attention has been paid on transaction cooperation in this context. Today, the transaction isolation provided by local DBMSs precludes cooperative transactions to be supported. This paper proposes a Cooperative Transaction Manager (CTM) to overcome this limitation. CTM provides a powerful transaction model supporting various structural dependencies between subtransactions. This model comes with a workspace management protocol to properly control cooperation between subtransactions. We show that this model can be easily emulated on top of standard DBMSs supporting the levels of isolation defined in SQL. CTM can be integrated in client/server, distributed and heterogeneous environments while preserving the autonomy of existing DBMSs.