This paper describes an architecture for sharing data in XML format through a peer-to-peer (P2P) network, which interconnects devices ranging from high-end servers to mobile devices. The XOP architecture allows devices with low storage capacity and subject to disconnection to use other peers of the P2P network for storing data. Users are able to locate and access data in a friendly and flexible way. Shared data is described using an extensible ontology, built using the OWL language, in order to provide more precise search results. This paper also describes a prototype of this architecture and analyzes the obtained performance.