The multimedia information exchanges in dis- tributed collaborative applications may be modeled, from communication system perspective, as the flow of media messages between user entities, to provide access to shared window objects on workstations. An example of shared window is a design document inter- actively reviewed by a team of engineers over a dis- cussion session. A key requirement is that all users should see the same local copy of a shared window object at any given point in time (WYSIWIS), even though these users may reside in different workstations interconnected over a network. In this paper, we study the temporal ordering of real-time persistent messages as the basis for achieving WYSIWIS. The approach requires specifying the synchronization constraints on accessing shared window objects in the form of state- transition relations and timeliness needs when process- ing messages for object state updates. Non-conflicting actions can be processed in any sequence by user en- tities, thereby increasing overall system-level perfor- mance and user-level efficacy. The paper describes the salient features of our concurrency control model, and then identifies the basic protocol elements to re- alize the model. Applications are also described to demonstrate the viability of our approach.