Michelle - Petri net program
(02/01/22) (proof of concept - PNML via JDOM, a possible Swing
implementation with MDI) - run "java ProgramDemo"
Michelle - Aquarium
program (02/01/21) (proof of concept - XML access via
JDOM) - Don't look at this one for the Swing code! main() and
printContents() are the most informative.