Operation-based versus State-based Merging in Asynchronous Graphical Collaborative Editing

In this paper we present and compare two approaches for asynchronous communication in object-based collaborative graphical editing. The operations allowed to be performed on the shared graphical document are not only simple operations such as create, delete, move, change colour or position, but also group/ungroup operations. We present an operation-based merging approach that was also used in a real-time mode of collaboration, as well as a state-based merging approach and compare the two approaches. The private working space can be synchronised against a central repository or against another private workspace.