Indexes form the basis for a general set of applications based on multimedia. They provide the general facilities required for real-time media interaction and presentation. These facilities can be viewed as an architecture for operating on real-time media. In figure 9.18 an architecture for indexes is presented. At the two lowest levels are the data and the indexes themselves. For server purposes the data is either video, audio or whiteboard packets, with index entries for each packet. The next layer has the operations on the indexes. These operations include such things as creating an index element, selecting regions of an index, adding an annotation to an index element, an so on. The top level of the architecture has applications. These do operations on indexes to achieve media recording or media playback.