What should transactions provide for CSCW applications?

As more and more CSCW applications are adopted by various organizations, their reliability becomes more and more important. In traditional database applications, the concept of transaction as well as serializability guarantees the success of the applications. However, it is widely accepted that a traditional transaction model with ACID (Atomicity, Consistency, Isolation and Durability) properties is not applicable to cooperative applications. Though many advanced transaction models have been proposed to address the problems, they are too centered around the databases to be useful in real environments. We analyze the requirements of various applications and review the existing advanced transaction models. Based on them, we explain what transactions have to provide to support CSCW applications.