Processing SPARQL Property Path Queries Online with Web Preemption

Abstract

SPARQL property path queries allow to write sophisticated navigational queries on knowledge graphs (KGs). However, the evaluation of these queries on online KGs are often interrupted by fair use policies, returning only partial results. SaGe-Path addresses this issue by relying on the concept of Partial Transitive Closure (PTC). Under PTC, the graph exploration for SPARQL property path queries is limited to a predefined depth. When the depth limit is reached, frontier nodes are returned to the client. A PTC-client is then able to reuse frontier nodes to continue the exploration of the graph. In this way, SaGe-Path follows a pay-as-you-go approach to evaluate SPARQL property path queries. This demonstration shows how queries that do not complete on the public Wikidata SPARQL endpoint can complete using SaGe-Path. An extended user-interface provides real-time visualization of all SaGe-Path internals, allowing to understand the approach overheads and the effects of different parameters on performance. SaGe-Path demonstrates how complex SPARQL property path queries can be efficiently evaluated online with guaranteed complete results.

Join Ordering of SPARQL Property Path Queries

“…in (A, P 17, ?x3) G1 tp 1 picking t 3 = (D, P 361, Q27611) in (D, P 361, Q27611) G1 γ 2 tp 3 picking t 1 = (B, P 641, Q3609) in (?x1, P 641, Q3609) G1 In this example, P (γ 1 ) = 1 2 × 1 1 × 1 1 = 1 2 , while P (γ 2 ) = 0. Indeed, when it becomes impossible for a random walk γ to sample t i for some i ≤ n, e.g.…”

“…Other approaches rely on innovative property path pattern operators [33,27,4,32,1]. For instance, to find the best strategy to evaluate a property pattern, Waveguide [33] introduces a new operator that mixes idea from relational and graph databases.…”

“…maintenance of the index. Other works propose new dedicated operators to process transitive closures [33,27,4,32,1]. Such approaches are very effective but focus on evaluating property path patterns (PPPs) alone, while most of the time PPPs are just part of a PPQ.…”