Abstract. In this paper, we propose a Java-based collaborative authoring system for multimedia presentation. Our system is composed of an Editing System, a Media Object Manager and a Collaboration Manager. The Editing System contains two unique editors; a 3D Spatio-Temporal editor and a Temporal Relation Network (TRN) editor, in addition to the traditional editors such as timeline editor, tag editor, attribute editor, and text editor. These editors are all shared over the Internet and together they form an easy and efficient multimedia authoring environment. Using our system, users in different places can author multimedia presentations in a unified spatio-temporal space while freely traversing the spatial domain and the temporal domain without changing the context of authoring. We also implemented some ideas for efficient concurrency control in our system. They are mainly based on user awareness, multiple versions, and access permissions of shared objects. Our work on the developmen...