We now know that various forms of distributed simulation are possible over the world-wide web. These include simple multiple replications of the same model, client-server architectures and distributed operation of one or more linked models. Like all web-based operations, these are slow due to current bandwidth limitations, but that could change in the next few years. Languages such as Java make this distributed work possible within standard web-browsers such as Internet Explorer and Netscape, though security considerations mean that this is not always straightforward. Component-based simulation stems from the ideas of object-orientation, which enable libraries of simulation based components to be developed for re-use. The development of the world-wide-web means that distributed component discrete simulation libraries in Java are now feasible. This paper reviews some of these developments and considers requirements for such distributed libraries, drawing on our experience at Lancaster.