Abstract
We present the theoretical foundation, the design and the implementation of a library, called EulerVC to interactively handle Euler diagrams for the purposes of resource management. Fast on-line algorithms to interpret wellformed diagrams have been developed utilising a new notion of marked points to keep track of the zone sets. The interface allows the construction of overlapping ellipses to represent categories together with the drag and drop of resources in order to categorise them. A visual indicator can be used to show if the diagram under construction is not wellformed to assist in reducing user mistakes, and sets of tags can be assigned to resources upon export. The generic approach is demonstrated via an integration with the bookmarking site del.icio.us.