BL: An Efficient Index for Reachability Queries on Large Graphs

Reachability query has important applications in many fields such as social networks, Semantic Web, and biological information networks. How to improve the query efficiency in directed acyclic graph ( DAG ) has always been the main problem of reachability query research. Existing methods either can't prune unreachable pairs enough or can't perform well on both index size and query time. In this paper, we propose BL ( Bridging Label ), a general index framework for reachability queries in large graphs. First, we summarize the relationships between BL and existing label indices. Second, we propose a kind of specific index, named minBL, which can avoid redundant labels. Moreover, we propose TFD-minBL and CTFD-minBL, which generate minBL under the TFD-based permutation single-pass and in incremental, respectively. Finally, we conduct a large number of extensive experiments on real and synthetic datasets. The experimental results show that our methods are much faster and use less storage overhead than the existing reachability query methods.