Process patterns allow the modular modelling and adaptable application of software processes. Present descriptions of process patterns show defects like non-uniform and unequivocal description forms and missing relationship definitions. These defects disadvantageously affect the effective usage of process patterns. In this work we present the language PROPEL (Process Pattern Description Language), which provides concepts for the semiformal description of process patterns and relationships between process patterns. With the help of PROPEL single process patterns can be modelled and, by definition of relationships, be composed to more complex processes. With the representation of different views of a process pattern catalog the process patterns and their relationships can be shown clearly. An example illustrates how a process pattern catalog and the contained process patterns are modelled. It is shown that in applying PROPEL the complexity of a process model can be reduced, the inconsistencies of
processes can be eliminated and the flexibility of processes can be improved
