Implementing a real-time decentralized collaborative editor using Php

Abstract

Collaborative editing systems (CESs) includes a class of distributed systems where users manipulate some shared objects like texts, images, XML documents, etc. To interact with each other. These systems are often based on data replication to improve data availability. There is a local copy of shared object for each user. Their local updated operations are propagated to other users. When updating the document, each user can see his own modifying as well as others’ at the same time. Operational Transformation (OT) approach is one approach used for ensure the convergence of replicated data. OT approach consists of a centralized / decentralized integration procedure and a transformation function called Inclusive Transformation (IT). The integration procedure is in charge of executing update operations, broadcasting local update operations to other sites, receiving update operations from other sites and determining transformations to be performed on a received operation before its execution. There are two kinds of integration procedures: centralized and decentralized. In the centralized integration, there is a central node, which ensures that all concurrent operations are executed in the same order at all sites. In the decentralized integration procedures, there is no central node and the operations may be executed in different orders by different sites. The decentralized integration procedures do not need any central server and then are more appropriate to P2P systems. There is a consistent IT function proposed. This project aims to study and choose a proper decentralized integration procedure from a group of researches. Then combining the integration procedure with IT function makes completed OT approach. Finally, write and implement a prototype based on open source wiki software XWiki to evaluate the consistency as well as overhead of the OT approach.