Pen Tablet UI
This describes the user interaction of the PenTablet. As of March 2008, this is actively being worked on by Patrick Dubroy.
1-to-1 Case
This describes the case when there is a 1-to-1 mapping between the PenTablet and the on-screen area that the tablet maps to. For example, an activity might allow the child to practice their penmanship. When the child writes on the tablet, the marks will shown inside a GTK widget which has the same aspect ratio, and is approximately the same size, as the physical PenTablet area.
The user interaction for this case should be fairly obvious.
Unconstrained drawing
This describes the case where the area that the user wishes to draw on is bigger and/or does not have the same aspect ratio as the physical PenTablet. The Draw activity is a good example of this case. One possible method of interaction has already been proposed here.