CristalView - The visualization of a Cristal A visualization of multiple overlapping hierarchical classification structures

At Statistics Netherlands (SN), the Dutch national statistics institute, statistical classifications are modeled using a complex structure of multiple overlapping hierarchical data structures in an abstract model called Cristal. The basic structure of this model is an hierarchical directed acyclic graph (DAG) that models the partwhole relations between the entities in statistical classifications, extended with another DAG structure that models the element-set relations between the entities in the classifications. In this thesis we provide a novel visualization technique composed of the treemap visualization technique and the Venn-diagram technique in combination with a force-directed layout algorithm in order to visualize the complex classification structures in a Cristal. Important aspects of the visualization are the combination of a hierarchical structure and a graph structure, as well as the usage of various perceptual cues that take advantage of the human visual perception system. Additionally, we have created a visualization tool that implements the proposed visualization technique. To test the functionality and usability of the visualization method, we have conducted a user experiment with a number of participants.