In a paper by Gostelow-Van Weert, it was shown that any processes can be described by Petri-nets (PN). Thus PN can be used as a model in the design (or analysis) of any computer system. This approach makes it possible to utilize all the theoretic knowledge developed for PN and thus provides a powerful tool for computer systems (or program) design. In this case, the PN can be used as a framework that provides a tool for: 1. the understanding of the design, 2. handling the incremental changes of the design (without redesigning the entire system), 3. the implementation of desired properties (like recoverability in case of failures, proper termination, mutual exclusion, etc.), and 4. at least, the analysis of the program in order to check if it has the desired properties.