Collaborative concurrency control of mobile devices using notiphores

A collaborative system enables multiple users to work together and share the same objects. This thesis addresses the problem of concurrent execution of tasks among multiple collaborating users and provides a mechanism to sustain concurrent access to the shared objects through notiphores (noti fication semaphores), a novel mechanism for collaborative mobile environments where constant connectivity with a central server is not guaranteed.;This thesis describes the first implementation of the notiphore concept and uses as example a mobile drawing application. Several algorithms are presented that outline the inner workings of a concurrency control system using notiphores and utilize user interaction to enhance concurrency. The notiphore mechanism provides a framework for injecting semantics such as contextual user roles and privileges to create effective and efficient conflict resolution policies. In addition, the integration of human intelligence can positively impact conflict resolution, and thereby enhance the concurrency in a collaborative system.;The described methods have been subject to thorough experimentation through simulation. The results reveal that the notiphore mechanism exhibits superior increase in concurrency compared to locking. Furthermore, the test results suggest that the notiphore mechanism can function as an integration platform for an application to incorporate various semantics to create differentiated concurrency control policies as needed by the application. In summary, this thesis presents the notiphore mechanism for concurrency control in a collaborative environment and proves its superiority over a conventional locking mechanism by conducting experiments measuring its efficiency, feasibility, flexibility, and most importantly increase in concurrent access of shared objects.