Lesson 2: Elements

Elements are on-screen representations of underlying concepts in the data set. Concepts are essentially attribute/value pairs (e.g., "quantity"/1000).

Elements can have a different look depending on what frame it is viewed in. For example, an element representing a city looks like a text label in the Outliner frame, but on the map it looks like a landmark, showing the element in terms of its logitude and latitude.

This is referred to as polymorphism. The element's appearance is determined by the frame in which it appears. Visage displays the appropriate element attributes for the various types of displays (e.g., map, plot, outliner).

Typically, elements in Visage are part of domain-specific databases. For purposes of this tutorial, we have connected to a generic "cities" database distributed with the Visage executable. You can begin accessing the database by dragging the DB Root data element from the bottom of the Tools frame to the Visage desktop or to another Visage frame.

Moving

Data elements can be dragged from one location to another.

1. Drag DB Root from the Tools frame to the desktop.
2. Open an Outliner frame (if necessary) by shift-dragging the Outliner icon from the Frames palette. Notice that it retains its appearance.
   

1. Drag DB Root from the Tools frame to the Outliner. When you release the mouse button, notice that the Outliner displays DB Root by its id.
   

1. Drag the "cities" element from the outliner to the workspace; the workspace is just a special type of frame. It can hold elements just like any other frame.
2. Now drag it back to the Outliner.

Copying

Moving elements in Visage is useful, but the real power lies in being able to copy data elements in order to view the same information in different frames. To copy an element, hold down the Shift key while dragging an element, and instead of moving the element, the element will be copied.

1. If you have only one Outliner frame open, open another one by shift-dragging it from the Tools frame..
2. Shift-drag the "cities" element from one Outliner to the other.
   

Notice that as you shift-drag, a second element appears on screen that you can move where you wish. You can also move it to the same Outliner, in which case you would have two elements representing the cities data set in the same Outliner. This is perfectly acceptable in Visage.

1. Make a copy of the "cities" element on the Visage workspace by shift-dragging one of the elements in the Outliner frame.
   
   

Notice that in this case, the element retains its appearance from the Outliner frame; contrast this with dragging the DB Root element (which is the same concept) to the workspace.

Selecting Elements

In Visage, multiple representations of the same data element can be copied to different frames to simultaneously show different views of the data. A powerful feature of Visage is that if there are multiple instances of a data element represented on screen, when one is selected the others are automatically selected as well.

1. If you followed the instructions in the previous section. you should now have three instances of the "cities" element.
2. Click on the different color chips in the Marking palette (the Marking palette is labeled "Paint" in older versions of Visage.
   

By clicking on the color chips, you are defining the selection color. The chosen selection color is identified by a narrow black border around the color chip.

1. Left click once on the "cities" element in one of the Outliners, and notice that its background is now filled with the current marking color. Notice that by clicking on the "cities" element in the first Outliner, the "cities" elements in both the second Outliner as well as the desktop are selected as well. They are all elements representing the same concept. The power of this feature will become clear later when we start working with several different types frames simultaneously.
   
   

1. Change the marking color to another color and click on the element again. Notice that the selection color changes for all three instances of the element.
   

Summary

Visage elements represent data concepts-collections of attribute/value pairs that can be viewed and manipulated through Visage. Elements can be created, moved, copied and selected.