Visualizing consumption in weighted hierarchies

Visualizing hierarchies is a recurrent topic in information visualization. Trees have been largely studied and are efficient to highlight the dataset structure. When a numerical value is attached to each node (weighted hierarchies), the enclosure-based methods such as treemaps appear to be powerful approaches. Surprisingly, hierarchies with nodes associated to consumable resources have been less studied and the existing approaches for visualizing hierarchies must admit some limitations from this perspective. However, such hierarchies are very common in practice (e.g. budget, storage disk quotas). This paper focuses on this specific problem and explores how the enclosure-based techniques can be adapted to represent two numerical values for each node: a quantity of available resources and the level of consumption of this resource. The approach proposed in the paper relies on the metaphor of storage tanks that are partially filled.