The RDF-3X engine for scalable management of RDF data

Abstract

RDF is a data model for schema-free structured information that is gaining momentum in the context of Semantic-Web data, life sciences, and also Web 2.0 platforms. The "pay-as-you-go" nature of RDF and the flexible patternmatching capabilities of its query language SPARQL entail efficiency and scalability challenges for complex queries including long join paths. This paper presents the RDF-3X engine, an implementation of SPARQL that achieves excellent performance by pursuing a RISC-style architecture with streamlined indexing and query processing.The physical design is identical for all RDF-3X databases regardless of their workloads, and completely eliminates the need for index tuning by exhaustive indexes for all permutations of subject-property-object triples and their binary and unary projections. These indexes are highly compressed, and the query processor can aggressively leverage fast merge joins with excellent performance of processor caches. The query optimizer is able to choose optimal join orders even for complex queries, with a cost model that includes statistical synopses for entire join paths. Although RDF-3X is optimized for queries, it also provides good support for efficient online updates by means of a staging architecture: direct updates to the main database indexes are deferred, and instead applied to compact differential indexes which are later merged into the main indexes in a batched manner.Experimental studies with several large-scale datasets with more than 50 million RDF triples and benchmark queries that include pattern matching, manyway star-joins, and long path-joins demonstrate that RDF-3X can outperform the previously best alternatives by one or two orders of magnitude.

Ultrawrap: SPARQL execution on relational data

“…These languages have spawned research into general purpose DBMS founded on the RDF graph model, triplestores, implemented as either native RDF triplestores [36,47] or RDF triplestores backed by SQL databases [13,22,28,48]. Ultrawrap is concerned with wrapping relational databases and using the existing SQL system to execute SPARQL queries on the relationally stored data without replicating the data to triplestores.…”

gStore: a graph-based SPARQL query engine

“…We report the number of triple insertions/deletions per second in gStore, and compare it with RDF-3x and x-RDF-3x in Table 2. RDF-3X had been extended for updates using the deferred-indexing approach [21] where the updates are first recorded into differential indexes, which are periodically merged into main indexes. x-RDF-3x employs the similar update strategy except for introducing "timestamp" of each triple [22].…”

QMDS: A File System Metadata Management Service Supporting a Graph Data Model-Based Query Language

“…There are several RDF triple stores, for instance, 4store [33] and RDF3X [34], which support the SPARQL language [35]. However, RDF is a different data model than what we are proposing in that RDF has only nodes and edges; there is no concept of an attribute.…”