In this paper we describe the design rationale of GANIMAM, a web-based syst
em which generates interactive animations of abstract machines from specifi
cations. Common principles of abstract machines come into play at three lev
els: the design of the specification language, the choice of graphical anno
tations to visualize higher-level abstractions and the use of the system to
explore and better understand known and detect new principles. (C) 2000 El
sevier Science B.V. All rights reserved.