Mobile computing devices, such as personal digital assistants and mobile phones, are becoming increasingly popular, smaller and more capable. We argue that mobile systems should be able to adapt to changing requirements and execution environments. Adaptation requires the ability to reconfigure the deployed code base on a mobile device. Such reconfiguration is considerably simplified if mobile applications are component-oriented rather than monolithic blocks of code. We present the Satin (System Adaptation Targeting Integrated Networks) component meta model, a lightweight local component meta model that offers the flexible use of logical mobility primitives to reconfigure the software system by dynamically transferring code. The meta model is implemented in the Satin middleware system, a component-based mobile computing middleware that uses the mobility primitives defined in the meta model to reconfigure both itself and applications that it hosts. We demonstrate the suitability of \satin in terms of lightweightedness, flexibility and reusability, for the creation of adaptable mobile systems by using it to implement, port and evaluate a number of existing and new applications, including an active network platform developed for satellite communication at the European Space Agency. These applications exhibit different aspects of adaptation and demonstrate the flexibility of the approach and the advantages gained.