Exploration of Geographic Databases: Supporting a Focus+Context Interaction Style

We present results on the design of a visual interaction environment for GISs based on focus+context visualisation and details-on-demand data presentation. We consider databases consisting of spatially related collections of regions with features, hierarchically organised as a nested partition. Interaction processes generate views on the database, displayed by maps preserving topological properties. An efficient navigation hence requires the adoption of topological invariants for representing such views. Since each step of the interaction process modifies only a portion of the invariant, we propose an efficient approach which dynamically updates the current topological invariant.