Time- and Space-Efficient Regular Path Queries

We introduce a time- and space-efficient technique to solve regular path queries over labeled (RDF) graphs. We combine a bit-parallel simulation of the Glushkov automaton of the regular expression with the ring index introduced by Arroyuelo et al., exploiting its wavelet tree representation in order to efficiently reach relevant states of the product graph. Our algorithm is able to simultaneously process several automaton states, as well as several graph nodes/labels. Our experiments show that our approach uses 3–5 times less space than existing state-of-the-art systems, while generally outperforming them in query times (nearly 3 times faster than the next best, on average).