Visual Displays for Browsing RDF Documents

Hyperbolic browsers are motivated by the “Circle Limit IV” woodcut of M.C. Escher. The hyperbolic tree view was introduced in graph drawing by Lamping and Rao [2] who observed that large structures could be compactly displayed by projecting a tree onto a hyperbolic plane. The effect of the projection is that components appear diminishing in size and radius exponentially the further they move from the centre of the diagram. The arguments for the hyperbolic display are twofold: an order of magnitude more nodes of a tree can be rendered in the same display space and the focus is maintained on the central vertex of the display and its immediate neighbourhood. The hyperbolic view is particularly useful for hierarchical diagrams with large numbers of leaves and branches and where neighbourhood relationships are meaningful. Examples of the hyperbolic view are INXIGHT’s Star Tree1 and HYPERPROF2. Given that the pure hyperbolic geometric projection is patented, projection onto a sphere, and diminishing radial layout views are the drawing approaches we have experimented with. Recent interest in the Semantic Web has invigorated interest in programs that render ontological data sources (structured metadata) in the style of semantic networks well known in AI. The ONTOBROKER [1] project used a hyperbolic browser to view semantic relationships between frames in F-Logic. ONTORAMA traces its lineage to the ONTOBROKER3 Java source code, but the code has been substantially re-written since 1999. The ONTORAMA effort involved refactoring the Java for the WEBKB-2 project [3, 4] which uses its own internal formats (conceptual graphs).