A novel concurrency control algorithm in distributed groupware

We present a new approach for solving the concurrency control problem in completely distributed collaborative applications. The main advantages of our approach are the simplicity of use and good responsiveness as there are no lock mechanisms. The general structure of the algorithm is application independent, which it makes it suitable for general collaboration frameworks. The algorithm applies to a set of applications that use tree as an internal data structure. This is not a serious constraint since many applications use XML (extensible Markup Language) for data representation and exchange and parsing XML documents results in tree structures. An example application of the algorithm is implemented in the DISCIPLE collaboration framework. The example applications are a group text editor and a whiteboard. We discuss the use of awareness widgets to increase the efficiency of collaborative work.