In a component-based approach for system design, one of the difficult problems is how to prove the correctness of the created components. Usually, the constituent components are supposed to be correct, i.e., possessing the desirable properties and being free from undesirable ones. However, the operators may destroy these properties or create new ones, resulting in an undesirable new component. Hence, every created component has to go through a new process of verification. This indeed involves a tremendous amount of effort! This book presents a component-based methodology for the creation and verification of design specifications. The methodology is formally presented as an algebra called Property-Preserving Petri Net Process Algebra (PPPA). Briefly, PPPA includes five classes of operators. The authors show that every operator of PPPA can preserve a large number of basic system properties. Hence, if the initial set of primitive components satisfies some of these properties, the created components will also ?automatically? satisfy them without the need of further verification. This greatly saves the efforts spent in verification.