"Principle of Petri nets" is the ultimate guide for understanding the fundamental principles of Petri nets and their potential applications. The book provides a detailed introduction to basic concepts such as global time, global state, and global control, and demonstrates how they relate to effective modeling of complex systems. Especially, the book covers the critical concepts of net system hierarchy formed with net folding and various methods for system analysis to give readers the tools they need to create and test effective models. This book's extensive application examples, including N-lift control, business process modeling, and a three-layer model for business process management (BPM), offer readers invaluable real-world insights and practical knowledge. Moreover, the book includes coverage of key topics such as concurrent nets (C-nets) that introduce data types into nets, general net theory like synchrony, enlogy (net logic), net topology, concurrency axioms, and information systems for reversible information transfer. This book is an essential reference for students, researchers, and professionals interested in enhancing their understanding of Petri nets, systems design, and other complex processes.