Grouping in collaborative graphical editors

Abstract

Often collaborative graphical systems lag behind well accepted single-user applications in terms of features supported. The frequently used operations of group/ungroup offered by almost every single-user graphical editor have not been considered by the collaborative graphical editing systems that try to preserve the intentions of the users involved in the concurrent editing. In this paper we present a novel algorithm based on operation serialisation for consistency maintenance in collaborative graphical editing dealing not only with simple operations such as create, delete, move, change colour or position, but also with group/ungroup operations. Based on the classification of conflicts into real and resolvable, an undo/redo mechanism is used in order to re-execute the operations in an imposed serialisation order.