This book constitutes the refereed proceedings of the 21st International Conference on Application and Theory of Petri Nets, ICATPN 2000, held in Aarhus, Denmark, in June 2000. The 20 revised full papers presented together with four invited surveys and four presentations were carefully reviewed and selected from 57 submissions. The papers address various aspects of Petri net research and development including system design and verification, UML, compositionality, process algebras, model checking, computer networking, business process engineering, communication networks. Various classes of...