Book excerpt: This book gives a Petri net based solution to the challenge of simulation, analysis and verification of parallel programs. The presented formal definition of compositional high-level Petri net semantics for B(PN)2 (Basic Petri Net Programming Notation) programs and SDL (Specification Description Language) systems allows the correct and efficient translation of also recursive procedures (in B(PN)2 and SDL) and processes with dynamic creation and termination (in SDL) into high-level Petri nets. All related issues are covered: 1. The algebra of M-nets is extended 2. References relating parts of the programs with parts of the resulting nets are introduced 3. Its implementation in the PEP tool is described 4. Examples (including verification) are given 5. An extension to hybrid systems is shown