In this book several concepts with respect to the development and reusability of multimedia content in web-based learning systems are introduced. More specifically, the development of a component-based framework that enables developers to employ reusable software components enhanced with metadata, creating complete instructional visualizations for a given subject and integrating these visualizations in an appropriate learning context, is discussed. Two activities for making stand-alone visualizations group-aware are addressed: transparent sharing of the same instructional visualization with...