New Algorithms and Methods for Collaborative Co-Editing Using HTML DOM Synchronization

The optimistic consistency control method known as Operational Transformation (OT) has been studied by researchers for nearly three decades, with centralized versions lying at the heart of most real-time web co-editing tools in academia and industry. Concurrent document editing is now a "must-have" for the modern workplace, with proven benefits in team productivity and efficiency. Once limited to primitive insert and delete operations, OT algorithms have evolved to support hierarchical data structures such as XML in order to meet the increasingly complex requirements of present-day collaborative applications. However, previous approaches have not focused on the changes that web applications enact upon the Document Object Model (DOM) of the Hypertext Markup Language (HTML) standard. This paper will present a feedback-based real-time architecture that allows arbitrary DOM-based document replicas to remain consistent by defining a new set of operations that preserve the user's editing intentions. The control loop of the architecture enables simultaneous DOM-based modifications by using novel conflict resolution algorithms and methods that bring "Virtual DOM" concepts together with state-of-the-art OT principles to enable advanced operations such as moving, splitting and merging of hierarchical DOM nodes. Through the implementation and evaluation of a rich-text editor, it will be shown how the architecture facilitates and accelerates the development of multi-user interactive web applications that meet today's demanding latency, scalability and accessibility requirements.