Interacting with Geographic Databases: a Focus+Context Approach

We present results on the design of a visual interaction environment for Geographic Information Systems, with focus on support of navigational tasks. We envision an exploration of the database where, starting from an abstract view, more and more detailed information is successively disclosed on demand, and visualized in a fish-eye view fashion. The interaction process is a sequence of views on the database, each displayed by a map in which topological properties are preserved. An efficient navigation requires the adoption of topological invariants for representing such partitions. These invariants might be computed from scratch at each step by using algorithms known in the literature. Since each interaction step modifies only a portion of the current topological invariant, we propose an efficient {\em incremental approach}, to update the current topological invariant by exploiting knowledge coming from previous steps, instead of recomputing always everything from scratch. This approach is mainly based on the formalization of the interaction process starting from the notion of "nested partition" of a spatial database