"The only constant is change" is an often cited phrase. We regard it as predominant for the area of process based information systems. In this paper we investigate how evolution of process based information systems can be supported by a process modeling framework that easily can be adjusted to changing requirements of an application domain. Our key contribution is the provision of a system infrastructure that supports the adaptation of both process modeling languages and process models to evolving application requirements. Our approach is based on a multi level meta modeling framework.