Petri nets do not designate a single modeling formalism. In fact, newcomers to the field confess sometimes to be a little puzzled by the diversity of formalisms that are recognized under this "umbrella". Disregarding some extensions to the theoretical modeling capabilities, and looking at the level of abstraction of the formalisms, Condition/Event, Elementary, Place/Transition, Predicate/Transition, Colored, Object Oriented... net systems are frequently encountered in the literature. On the other side, provided with appropriate interpretative extensions, Controled Net Systems, Marking Diagrams (the Petri net generalization of State Diagrams), or the many-many variants in which time can be explicitly incorporated -Time(d), Deterministic, (Generalized) Stochastic, Fuzzy...- are defined. This represents another way to define practical formalisms that can be obtained by the "cro- product" of the two mentioned dimensions. Thus Petri nets constitute a modeling paradigm, understandable in a broad sense as "the total pattern of perceiving, conceptualising, acting, validating and valuing associated with a particular image of reality that prevails in a science or a branch of science" (Thomas S. Kuhn).
From the reviews of the first edition:
"The book represents an excellent guide for learning, teaching and developing researches in the field of Petri nets (PNs). ... the authors provide complex material, gradually structured, which ensures its efficient utilization at different levels of knowledge. Thus, the book is highly recommended to a large group of potential readers, from undergraduate students who want to become acquainted with the fundamental concepts, to PhD students and research fellows who are interested in the most recent progress of theory and applications." (Octavian Pastravanu, Zentralblatt MATH, Vol. 1074, 2005)
"The book represents an excellent guide for learning, teaching and developing researches in the field of Petri nets (PNs). ... the authors provide complex material, gradually structured, which ensures its efficient utilization at different levels of knowledge. Thus, the book is highly recommended to a large group of potential readers, from undergraduate students who want to become acquainted with the fundamental concepts, to PhD students and research fellows who are interested in the most recent progress of theory and applications." (Octavian Pastravanu, Zentralblatt MATH, Vol. 1074, 2005)