Expressive languages for path queries over graph-structured data

For many problems arising in the setting of graph querying (such as finding semantic associations in RDF graphs, exact and approximate pattern matching, sequence alignment, etc.), the power of standard languages such as the widely studied conjunctive regular path queries (CRPQs) is insufficient in at least two ways. First, they cannot output paths and second, more crucially, they cannot express relations among paths. We thus propose a class of extended CRPQs, called ECRPQs, which add regular relations on tuples of paths, and allow path variables in the heads of queries. We provide several examples of their usefulness in querying graph structured data, and study their properties. We analyze query evaluation and representation of tuples of paths in the output by means of automata. We present a detailed analysis of data and combined complexity of queries, and consider restrictions that lower the complexity of ECRPQs to that of relational conjunctive queries. We study the containment pro...

• Type: Conference
• Year: 2010
• Where: PODS
• Authors: Pablo Barceló, Carlos A. Hurtado, Leonid Libkin, Peter T. Wood
• Keywords: Database, Output Paths, PODS 2010, Regular Path Queries, Relational Conjunctive Queries