GridVine is a semantic overlay infrastructure based on a peer-to-peer (P2P) access structure. Built following the principle of data independence, it separates a logical layer — in which data, schemas, and schema mappings are managed — from a physical layer consisting of a structured P2P network supporting decentralized indexing, key load-balancing, and efficient routing. The system is decentralized, yet fosters semantic interoperability through pair-wise schema mappings and query reformulation. GridVine’s heterogeneous but semantically related information sources can be queried transparently using iterative query reformulation. The authors discuss a reference implementation of the system and several mechanisms for resolving queries collaboratively.