[*] Università degli Studi di Milano, Dipartimento Scienze Informazione, Via Comelico 39, 20135 Milano, Italy.
[1] RMG is a tool kit for authoring of visualization courseware, by C.Young of HP labs.
[2] UNIX is a trademark of Bell Laboratories, Murray Hills, NJ 07974.
[3] Objective-C is a trade name of StepStone Corporation, Sandy Hook, CO 06482.