HT: A Novel Labeling Scheme for k-Hop Reachability Queries on DAGs

Abstract

Given a directed acyclic graph (DAG), a k-hop reachability query u →?k is used to answer whether there exists a path from u to v with length < k. Answering k-hop reachability queries is a fundamental graph operation and has been extensively studied during the past years. Considering that existing approaches still suffer from inefficiency in practice when processing large graphs, we propose a novel labeling scheme, namely HT, to accelerate k-hop reachability queries answering. HT uses a constrained 2hop distance label to maintain the length of shortest paths between a set of hop nodes and other nodes, and for the remaining reachability information, HT uses a novel topological level to accelerate graph traversal. Further, we propose to enhance HT by two optimization techniques. The experimental results show that compared with the state-of-the-art approaches, HT works best for most graphs when answering k-hop reachability queries with small index size and reasonable index construction time.