Answering Property Path Queries over Federated RDF Systems

Ningchao Ge, Peng Peng, Jibing Wu, Lihua Liu, Haiwen Chen, Tengyun Wang

Abstract: Property path query can get graph nodes meeting complex conditions with more concise expressions for some SPARQL basic graph patterns, which is an important new query type in SPARQL 1.1. However, property path query is only applied in centralized RDF system, not in a federated RDF system. In this paper, a MinDFA-based property path query method over federated RDF system is proposed, called FPPQO (Federated Property Path Query Optimization). FPPQO first decomposes a federated property path query into multiple subqueries. Then, a Thompson-based MinDFA algorithm is used to construct MinDFA corresponding to the property path expression of each subquery. Finally, the query execution strategy base on B-DFS is used to search for MinDFA matching. During the matching process, the possible circular matching problem is eliminated by adopting the alternating buffer marking mechanism. Experimental results on datasets of different sizes show that the proposed scheme is effective and scalable.