Join Size Estimation on Boolean Tensors of RDF Data

The Resource Description Framework (RDF) represents information as subject--predicate--object triples. These triples are commonly interpreted as a directed labelled graph. We instead interpret the data as a 3-way Boolean tensor. Standard SPARQL queries then can be expressed using elementary Boolean algebra operations. We show how this representation helps to estimate the size of joins. Such estimates are valuable for query handling and our approach might yield more efficient implementations of SPARQL query processors.