Pervasive computing envisions environments where computers are blended into our environment to provide services. This vision is today very popular and a number of pervasive platforms are already used today in smart homes or smart plants. These platforms however are based on different middleware and networks. Interoperability has recently emerged as a key issue. Interoperability is a difficult problem which requires interactions between platforms that were not designed to do so. It demands to be able to communicate but also to share contextual information on demand. We here present an architecture to federate platforms and a solution to autonomically manage context at the platform level. This is demonstrated in the smart home domain and, more precisely, with the iCasa/iPOJO and Base pervasive platforms.