<p>Answering reachability queries is a fundamental operation in graph theory. Existing methods either build an index for partial reachability, which may lead to costly graph traversal during query processing, or construct an index for complete reachability, which can be inefficient when handling queries involving unreachable vertex pairs, as it requires comparing full vertex labels. Most reachability methods focus on regular directed acyclic graphs (DAGs). In this paper, we introduce Mix Labeling for Reachability Queries (MLRQ), a novel approach specifically designed for reduced DAGs, which preserve the essential structural properties of regular DAGs while being smaller. MLRQ utilizes topological labels consisting of two integers to filter a considerable portion of unreachable vertex pairs effectively. Additionally, MLRQ incorporates 2-hop labels and spanning tree intervals to cover the complete reachability relationship, thereby improving query efficiency and avoiding graph traversal. We also propose optimization strategies to further improve performance. Our experimental results demonstrate that MLRQ performs optimally in answering reachability queries for the majority of graphs.</p>

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MLRQ: an efficient labeling scheme for reachability queries on reduced DAGs

  • Haiyan Zhang,
  • Keng Hoon Gan,
  • Shengping Yang

摘要

Answering reachability queries is a fundamental operation in graph theory. Existing methods either build an index for partial reachability, which may lead to costly graph traversal during query processing, or construct an index for complete reachability, which can be inefficient when handling queries involving unreachable vertex pairs, as it requires comparing full vertex labels. Most reachability methods focus on regular directed acyclic graphs (DAGs). In this paper, we introduce Mix Labeling for Reachability Queries (MLRQ), a novel approach specifically designed for reduced DAGs, which preserve the essential structural properties of regular DAGs while being smaller. MLRQ utilizes topological labels consisting of two integers to filter a considerable portion of unreachable vertex pairs effectively. Additionally, MLRQ incorporates 2-hop labels and spanning tree intervals to cover the complete reachability relationship, thereby improving query efficiency and avoiding graph traversal. We also propose optimization strategies to further improve performance. Our experimental results demonstrate that MLRQ performs optimally in answering reachability queries for the majority of graphs.