“Hypermedia applications tend to use simple representations for navigation: most commonly, nodes are organized within an unconstrained graph, and users are presented with embedded links or lists of links. Recently, new data structures have emerged which may serve as alternative models for both the organization, and presentation, of hypertextual nodes and links. In this paper, we consider zzstructures, mSpaces, and polyarchies from the perspective of graph theory, and compare these models formally.” – (Michael J. McGuffin and M.C. Schraefel) – courtesy of ui designer