In: Kurt Jensen (Ed.): Proc. of the Fourth International Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, Aarhus, Denmark, August 28-30, 2002, pages 39-58. Technical Report DAIMI PB-560, August 2002. Available online: http://www.daimi.au.dk/CPnets/workshop02/cpn/papers/.