EVolve: An Extensible Software Visualization Framework

classes are shown in rounded boxes, concrete classes in plain boxes. Overridden methods are shown in italics, concrete methods in plain text. Abstract classes provide functionality that all visualizations in the subtree have in common. Visualization declares two methods which all visualizations share: sort (allows data to be sorted) and makeSelection (allows the user to select a subset of data to be re-colored or revisualized) XYVisualization declares two methods: installPainter (defines the color scheme used in the visualization) and mouseMove (determines the text that appears when the user moves mouse over a particular part of the visualization). Depending on the way that coordinates on xand y-axis are treated, XYVisualization has three variations: • Value-Reference visualizations contain a reference on one axis. They share mouseMove and sort • Reference-Reference visualizations contain a reference on both x and y axes. They share mouseMove, sort and makeSelection • Value-Value visualizations contain a value on both x and y axes. This variation is more open-ended, only sort is shared and all other methods are overridden. 3.2 Barchart A bar chart (Figure 7) is a Value-Reference visualization. The reference axis (y-axis) shows 882 method invocation locations, each location has its own unique color. The x-axis shows the