There are many different process meta-models that offer different viewpoints of a same process: activity oriented, product oriented, decision oriented, context oriented and strategy oriented. However, the complementarity between their concepts is not explicit and there is no consensus about the concepts themselves. This problem leads to inadequate process meta-models with organization needs, so the instantiated models do not correspond to the specific demands and constraints of the organizations or projects. However,, method engineers should be able to build process metamodels according to the specific organization needs. We propose a method to build unified, fitted and multi-viewpoints process meta-models. The process engineering method is based on a process domain model and on patterns.