Although powerful, the transaction model adopted in traditional database systems is found lacking in functionality and performance when used for applications that involve reactive, long-lived and collaborative activities. The following are some of the issues that arise in the context of the extended transaction models that have been proposed to address this lack: correctness properties of a model vis a vis visibility, consistency, recovery, and permanence (e.g., traditional transactions guarantee failure atomicity, serializability, and permanence.); similarities and differences between two transaction models; constraints on using two models in conjunction; and, mechanisms needed for managing extended transactions. These issues motivated the development of ACTA, a comprehensive formalism which characterizes the effects of transactions on each other and on objects in the database. ACTA's ability to deal with existing extended transaction models and correctness notions is indicative of its generality. The need for extended transactions emerges from the demands of applications, such as CAD/CAM, software development environments, object-oriented databases, and distributed operating systems. By providing a formal framework in which to capture the properties of extended transactions, and thereby identifying the needed transaction management mechanisms, this work is producing results that will impact these information-intensive application areas.
