R2DB: A System for Querying and Visualizing Weighted RDF Graphs

Existing RDF query languages and RDF stores fail to support a large class of knowledge applications which associate utilities or costs on the available knowledge statements. A recent proposal includes (a) a ranked RDF (R2DF) specification to enhance RDF triples with an application specific weights and (b) a SPA Rank QL query language specification, which provides novel primitives on top of the SPARQL language to express top-k queries using traditional query patterns as well as novel flexible path predicates. We introduce and demonstrate R²DB, a database system for querying weighted RDF graphs. R²DB relies on the AR2Q query processing engine, which leverages novel index structures to support efficient ranked path search and includes query optimization strategies based on proximity and sub-result inter-arrival times. In addition to being the first data management system for the R2DF data model, R²DB also provides an innovative features-of-interest (FoI) based method for visualizing large sets of query results (i.e., sub graphs of the data graph).