Empirical studies of an abstract semantic model, augmented transition network (ATN), with Object Composition Petri Net (OCPN) to model multimedia presentations are performed in this paper. An ATN consists of a set of states and directed arcs and uses a regular expression as its input. The advantages to use a regular expression are its simplicity and ease of modification. Simulation experiments to compare ATN and OCPN are performed in this paper. The results show that ATN requires fewer nodes and arcs to represent a multimedia presentation than OCPN does. These results indicate ATN handles on-line multimedia presentations more efficient and requires less precious main memory space.