In this paper we describe a novel adaptation architecture as well as a process for the development of policy based adaptive services for mobile commerce. Our architecture is based on three basic requirements and defines the four core elements: context, policies, policy decision point and policy enforcement point. The proposed approach is based on the reuse and adaptation of existing and matured standards, APIs and middleware for representing context information, usage of policies for reasoning and for the communication between the involved parties. Our aim is to present a simple architecture taking as much as possible available work and software into account to support the rapid development of context aware mobile services. Furthermore we present a novel methodology for the definition of context information and policies that is supported by a new UML based diagram and a module pipeline. We show the feasibility of the architecture as well as of the process based on a prototype which implements a typical scenario for an adaptive mobile service.