Analysis of the Effect of Query Shapes on Performance over LDF Interfaces

The adoption of Semantic Web technologies, and in particular the Open Data initiative, has contributed to the steady growth of the number of datasets and triples accessible on the Web. Most commonly, queries over RDF data are evaluated over SPARQL endpoints. Recently, however, alternatives such as TPF have been proposed with the goal of shifting query processing load from the server running the SPARQL endpoint towards the client that issued the query. Although these interfaces have been evaluated against standard benchmarks and testbeds that showed their benefits over previous work in general, an evaluation of the effects of the query shapes on query performance of the different available interfaces has never been done. In this paper, we present the results of our in-depth evaluation of query shapes impact on the performance of existing LDF interfaces. Using representative and diverse query loads that are designed to include relevant query shapes and are based on the query log of a public SPARQL endpoint, we stress test the different interfaces and identify their strengths and weaknesses.