An Efficient Synchronous Collaborative Editing System Employing Dynamic Locking of Varying Granularity in Generalized Document Trees

The primary goals in a synchronous collaborative editing system (CES) involve ensuring a high level of concurrent access while maintaining the properties of the CCI model. We revisit the idea of applying lock-based concurrency control algorithms to manage access to a shared document; this research overcomes the traditional problem of reduced concurrent access inherent in pessimistic concurrency control by dynamically managing the size of the portion of document locked based upon user demand, scaling up and down the lock granularity to accommodate user write requests. We present algorithms to efficiently maximize concurrent access while utilizing caching techniques to reduce communication costs. We also discuss how OT and other optimistic concurrency control techniques may be incorporated within our approach - leveraging best practices of both techniques. We conclude with an analysis of the communication and computational costs of our approach and compare these costs to costs incurred using OT-based concurrency control