This article presents an ontology-based peer-to-peer network that facilitates efficient search for data in widearea networks. Data with the same semantics are grouped together into one-dimensional semantic ring space in the upper-tier network. This is achieved by applying an ontology-based semantic clustering technique and dedicating part of node identifiers to correspond to their data semantics. In the lower-tier network, peers in each semantic cluster are organized as Chord identifier space. Thus, all the nodes in the same semantic cluster know which node is responsible for storing context data triples they are looking for, and context queries can be efficiently routed to those nodes. Through the simulation studies, the authors demonstrate the effectiveness of our proposed scheme.