RDFPeers: A Scalable Distributed RDF Repository based on A Structured PeertoPeer Network

摘要

Centralized Resource Description Framework (RDF) repositories have limitations both in their failure tolerance and in their scalability. Existing Peer-to-Peer (P2P) RDF repositories either cannot guarantee to find query results, even if these results exist in the network, or require up-front definition of RDF schemas and designation of super peers. We present a scalable distributed RDF repository (“RDFPeers”) that stores each triple at three places in a multi-attribute addressable network by applying globally known hash functions to its subject, predicate, and object. Thus, all nodes know which node is responsible for storing triple values they are looking for, and both exact-match and range queries can be effi- ciently routed to those nodes. RDFPeers has no single point of failure nor elevated peers, and does not require the prior definition of RDF schemas. Queries are guaranteed to find matched triples in the network if the triples exist. In RDFPeers, both the number of neighbors per node and the number of routing hops for inserting RDF triples and for resolving most queries are logarithmic to the number of nodes in the network. We further performed experiments that show that the triple-storing load in RDFPeers differs by less than an order of magnitude between the most and the least loaded nodes for real-world RDF data.