The JOTSA animation environment. JOTSA (Java On-Time Synchronous Animation) is an environment for World Wide Web-based animation of algorithms and data. ”On-time” refers to the moving of objects so that they complete their movement at a known time, independent of the hardware or operating system of the target machine. ”Synchronous” refers to the coordination of the movement of several objects. JOTSA was motivated by the need to represent exact timing relationships in network protocols and other time-critical applications in a platform-independent manner. JOTSA provides a Web-based user interface which is a natural vehicle for remote execution and wide dissemination. In addition to exact-time animation, JOTSA supports multiple dependent or independent views, panning and zooming, linking of collections of objects, event-driven simulation and synchronization. Applications have the full resources of the Java Virtual Machine and can be written to support interaction in a way that is familiar to the user.