Browser-based collaborative modeling in near real-time

Collaboration on digital products - for instance in science, design or production - is typically being practiced using cumbersome means like sending document drafts back and forth among collaborators. Recent advances in Web technologies allow collaborators to synchronously edit artifacts. From an engineering perspective, adding (near) real-time, multi-user collaboration to single-user applications is a challenging task as it requires the implementation of features such as conflict resolution as well as propagation and visualization of updates in near real-time. In this paper, we present SyncLD, a collaborative system that was built for a community of practice on `learning design' to support Web-based, synchronous collaborative editing of learning design models. The system was built on widget technology and implements propagation of edits using inter-widget communication based on the Extensible Messaging and Presence Protocol (XMPP) as well as synchronization of edits using Operational Transformation algorithms. A system evaluation shows that the near real-time collaboration features work as intended, and an end-user evaluation demonstrates the usefulness and usability perceived by practitioners. The core near real-time features are bundled in an open-source library that can be reused for building applications for similar use cases, hopefully propelling the future availability and adoption of near real-time collaboration as a standard feature in Web applications.