faceted classification systems

Overview diagrams are one of the best tools for orientationand navigation in hypermedia documents [17]. By present-ing a map of the underlying information space, they allowthe users to see where they are, what other information isavailable and how to access the other information. How-ever, for any real-world hypermedia system with many nodesand links, the overview diagrams represent large complexnetwork structures. They are generally shown as 2D or 3Dgraphs and comprehending such large complex graphs is ex-tremely difficult. The layout of graphs is also a very difficultproblem [1].