Recent technology advances have made computer-based multimedia cooperation among distributed users feasible. Joint-Viewing (JV) is one such proposed cooperation concept. Correct interaction in it requires synchronization at various levels. In this paper we focus on synchronization aspects on the data stream level. We present several JV scenarios and state for each of these requirements concerning interstream synchronization. Then we introduce basic abstractions of a synchronisazion scheme which is powerful enough to model a variety of JV configurations with their various synchronization needs. The presented scheme is based on the notion of a referencing system which consists of a set of logical clocks each defining a different time zone in the referencing system. Logical clocks provide timing information for input and output devices which are used to produce and consume data in a synchronized fashion.