Setup

occurs when the query previewer passes control to the DQI. During setup, the widgets, starfield display, bars, and charts are initially drawn on the screen. The DQI reads the active subset. In addition, it makes a copy of the active subset and re-scales each attribute to the range [1,p] where p is the number of pixels in the attribute's range slider. This step is important because we need this re-scaled information frequently. Because setup occurs infrequently, we can allow several seconds for it.