A less constraint concurrency control and consistency maintaince in collaborative CAD system

One difference between real-time CSCW systems and traditional distributed systems is that the former one needs to provide a natural, free and fast interface for multi-user interaction. However, typical multi-user interaction methods in 3D CAD systems apply strict consistency maintenance, such as lock mechanism and floor control which result in a stagnant and unnatural interface. This article proposes a semantic-based operational transformation (OT), which is similar to the traditional OT form, to support less constraint multi-user interaction and to achieve consistency in collaborative CAD editing (co-CAD) systems. Major technical contributions of this article include: a 3D semantic priority to select operations from waiting list, an OT strategy to decide OT direction, OT rules and a kernel OT function for co-CAD systems.