19. Building Hierarchical Cybermaps
The model described so far is only of limited use for extremely large hyperdocuments with thousands or even millions of nodes because there is only one CYBERMAP for the whole hyperdocument. This means that one hyperdrawer has to represent hundreds or even thousands of nodes. In this case, CYBERMAP offers a usable overview of the whole hyperdocument, but it can no longer directly be used for navigation purposes. The interest list still offers a viable mechanism to get direct access to the most interesting nodes. Fortunately, it is straightforward to extend our technique by introducing layers of CYBERMAPs where every sub-CYBERMAP only describes a small part of the document. Sub-CYBERMAPs have then to be subsumed in hyperdrawers of other CYBERMAPs resulting in a hierarchy of CYBERMAPs.