No abstract

Design applications, e.g., CAD or media production, often require multiple users to work cooperatively on shared data, e.g., XML documents. Using explicit transactions in such environments is difficult, because designers usually do not want to consider transactions or ACID. However, applying transactions in order to control visibility of changes or specify recovery units, is reasonable, but determining transaction boundaries must be transparent for the designer. For this reason we propose a novel approach for the automatic determination of transaction boundaries which considers the degree of cooperation designers want to achieve. Furthermore, we present an optimistic synchronization model based on the traditional backward oriented concurrency control (BOCC) algorithm, in order to synchronize the determined transactions in multiuser environments. It exploits the semantics of tree operations on XML data and enforces a correctness criterion weaker than serializability. As our evaluation shows, when multiple users work cooperatively on shared data, this model significantly reduces the number of transaction aborts in comparison to the traditional BOCC approach.

No abstract

In many application areas, for example in design or media production processes, several authors have to work cooperatively on the same project. Thereby, a frequently used data format is XML. In this paper, we address the special requirements of cooperative working on shared XML graph structures, such as early visibility of updates, multi-directional information flow, and parallel working. Since most existing transaction models are hardly applicable, we present a novel transaction model based on multi-level transactions and dynamic actions that meets these requirements. Additional advantages of this model are appropriate concepts for transaction synchronization and resolution of conflicts.

In many application scenarios, for example in design or media production processes, several authors have to work cooperatively on the same project and consequently on the same data. In this context, a frequently used data format is XML. To enable cooperative authoring of shared XML graph structures, several requirements have to be fulfilled, e.g., early visibility of updates, multi-directional information flow, and processing data in parallel. Most transaction models proposed in the literature are hardly applicable in this context. In this paper, we propose a novel transaction model based on multi-level transactions and dynamic actions that meets these requirements. We describe the transaction model as well as its formal properties and discuss issues such as synchronization and logging.