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PaxDB is a resource description framework (RDF) store based on Jena TDB.

Jena TDB is a popular open source RDF graph store. However, it is a single node, with no-fault tolerance and high availability. PaxDB is a replicated RDF graph store that leverages an existing graph store and these replication technologies:

  1. Apache Jena TDB graph-store
  2. IBM FRAPP'E — a state of the art quorum-based replication

This combination results in a fault-tolerant, persistent RDF store. Based on a quorum system, PaxDB can withstand F failures out of 2F+1 replicas without losing availability and does not suffer a loss of data if the entire cluster is brought down. PaxDB is elastic, allowing for the easy addition and removal of replicas. Furthermore, since FRAPP'E, on which PaxDB is built, implements a configurable Paxos algorithm, these changes can be made without any down time.

The PaxDB API is very similar to the Jena TDB API and fully supports the Jena Dataset and SPARQL query APIs. The main use case for PaxDB is as a service registry in the EU-funded COMPOSE project.