Figure 11: Example query with DEVise visualization (click on image for larger version)
The DEVise visualization presents the results of a query as a plot and is thus similar to the plots visualization method. In addition, it provides two additional features: a) the ability to zoom in/out to parts of the plot, and b) the ability to attach extra values to each point of the plot. This method is activated by clicking on the DEVise Visualization Tool . The user uses the x-axis /y-axis projection tools to select the fields that will appear in the plot, similar to the plot visualization; in addition, the Attach Value Tool allows a number of fields to be attached to each point in the plot, Figure 11 shows an example query, where the user is plotting Field.nChild on the x-axis, Field.nGalaxy on the y-axis and has also requested that the corresponding Field.nObjects and Field.nStars values be attached at each point of the plot.
Figure 12 shows the resulting plot window. Note that the window appears before the query is completed and is updated continuously with new results. The user can zoom in on a region of the plot by dragging a rubber band and can zoom-out by using the <Backspace> key. The attached values can be shown by clicking on a point of the plot, while holding down the <Shift> key.
The devise visualization window offers the following functionality:
Refresh
Re-execute the query that produced the plot and update the view with the new results.
Select
Select the query that generated these results. The query is selected in the history window and shown in the canvas.
Pause/Continue
Freeze the visualization in its current state. The corresponding query is paused and no new results are fetched from the database. By pressing the button again, the user causes the query to resume execution and the visualization is updated with the new results.
Stop
Stop the execution of the query. This cancels the query on the database server and the visualization is not be updated with any new results thereof. From this state, the user can only restart the visualization from the beginning with the refresh button.
For more information on DEVise, you can visit the DEVise website.