Exploratory data analysis is an iterative process where high level questions lead to specific queries whose answers are examined for interesting patterns. These in turn suggest new questions. To facilitate this kind of exploration, we would like to provide the analyst rapid, incremental, and reversible operations giving continuous visual feedback. However we also need the expressive power to reorganize the data on the fly, to juxtapose objects according to diverse criteria, and visualizations to show relationships among properties of these different objects. In short, we want both the ease of use of direct manipulation systems and the power of database query systems. This need is recognized, yet in current systems the architecture for connecting them is a feedforward batch stream from query to visualization system, each having a separate interface.

VQE is a Visual Query Environment for expressing queries involving navigation among multiple objects, aggregating these objects, and defining derived attributes for them. When combined with SAGE and SageBrush for creating visualizations, and Visage for their direct manipulation it offers:

• Navigation among sets of objects of different types.
• Visualization of attributes from multiple object types in a single graphic.
• UI techniques for assigning data attributes to be visualized to graphical properties.
• Extension of dynamic query filter techniques to control multiple objects sets.
• Coordination among visualizations derived from different queries.
• Dynamic definition of new data attributes.