ANNA: Answering why-not questions for SPARQL

Considerable effort has been made to improve the functionality and usability of SPARQL search engines. However, explaining missing items in the results of SPARQL queries or the so-called why-not questions remains in its infancy. Existing explanation models cannot be trivially extended to SPARQL queries because of the SPARQL-specific features in the data model and query operations. In this demonstration, we present a novel explanation system, ANNA (Answering why-Not questioNs for spArql), to explain why-not questions using a divide-and-conquer strategy. ANNA can visualize explanations to help users revise their initial queries to make the expected result-items presented. Experimental results on DBpedia prove that ANNA can generate high-quality explanations within a reasonable amount of time.