Diaforá: A Visualization Tool for the Comparison of Biological Taxonomies

We address the problem of visualizing differences between two versions of a biological taxonomy. Given the dynamics of the taxonomic work, taxonomists are often faced with alternative versions of a taxonomy that need to be reconciled. Nevertheless, visual comparison of hierarchies is an open problem that involves several difficult challenges in Visual Analytics. First, how to display not one but two possibly large taxonomies on a fixed-size screen. Second, how to highlight all differences between the two taxonomies. We present Diaforá, an interactive tool that infers and visualizes the differences. Automatic inference is achieved by incorporating taxonomy rules to identify operations such as merging, splitting, and renaming of taxa, among others. Highlighting of differences is accomplished by using the edge drawing technique, which has been enhanced with a number of features suggested by users of a prototype version. Diaforá has been implemented and tested with real world taxonomies such as Bryozoa and Annelida as well as with artificial taxonomies.