ABSTRACT
Querying RDF data is viewed as one of the main applications of graph query languages, and yet the standard model of graph databases -- essentially labeled graphs -- is different from the triples-based model of RDF. While encodings of RDF databases into graph data exist, we show that even the most natural ones are bound to lose some functionality when used in conjunction with graph query languages. The solution is to work directly with triples, but then many properties taken for granted in the graph database context (e.g., reachability) lose their natural meaning.
Our goal is to introduce languages that work directly over triples and are closed, i.e., they produce sets of triples, rather than graphs. Our basic language is called TriAL, or Triple Algebra: it guarantees closure properties by replacing the product with a family of join operations. We extend TriAL with recursion, and explain why such an extension is more intricate for triples than for graphs. We present a declarative language, namely a fragment of datalog, capturing the recursive algebra. For both languages, the combined complexity of query evaluation is given by low-degree polynomials. We compare our languages with relational languages, such as finite-variable logics, and previously studied graph query languages such as adaptations of XPath, regular path queries, and nested regular expressions; many of these languages are subsumed by the recursive triple algebra. We also provide examples of the usefulness of TriAL in querying graph and RDF data.
- S. Abiteboul, R. Hull, and V. Vianu. Foundations of Databases. Addison-Wesley, 1995. Google Scholar
Digital Library
- R. Angles and C. Gutierrez. Survey of graph database models. ACM Computing Surveys, 40(1), 2008. Google Scholar
Digital Library
- R. Angles. A comparison of current graph database models. In ICDE Workshops, pages 171--177, 2012. Google Scholar
Digital Library
- K. Anyanwu and A. Sheth. ρ-Queries: Enabling querying for semantic associations on the Semantic Web. In WWW'03, pages 690--699. Google Scholar
Digital Library
- M. Arenas and J. Pérez. Querying semantic web data with SPARQL. In PODS, pages 305--316, 2011. Google Scholar
Digital Library
- P. Barceló, L. Libkin, A.W. Lin, and P. Wood. Expressive languages for path queries over graph-structured data. ACM TODS 38(4) (2012). Google Scholar
Digital Library
- P. Barceló, D. Figueira, and L. Libkin. Graph logics with rational relations and the generalized intersection problem. In LICS'12, pages 115--124. Google Scholar
Digital Library
- P. Barceló, J. Pérez, and J. L. Reutter. Relative expressiveness of nested regular expressions. In AMW'12, pages 180--195.Google Scholar
- P. Barceló, J. Pérez, and J. L. Reutter. Schema mappings and data exchange for graph databases. In ICDT'13. Google Scholar
Digital Library
- D. Calvanese, G. De Giacomo, M. Lenzerini, and M.Y. Vardi. Containment of conjunctive regular path queries with inverse. In KR'2000, pages 176--185.Google Scholar
- D. Calvanese, G. De Giacomo, M. Lenzerini, and M.Y. Vardi. Rewriting of regular expressions and regular path queries. JCSS, 64(3):443--465, 2002.Google Scholar
Digital Library
- M. Consens, A. Mendelzon. GraphLog: a visual formalism for real life recursion. In PODS'90, pages 404--416. Google Scholar
Digital Library
- I. Cruz, A.O. Mendelzon, and P. Wood. A graphical query language supporting recursion. In SIGMOD'87, pages 323--330. Google Scholar
Digital Library
- P. Cudré-Mauroux and S. Elnikety. Graph data management systems for new application domains. PVLDB, 4(12):1510--1511, 2011.Google Scholar
Digital Library
- W. Fan, J. Li, S. Ma, N. Tang, and Y. Wu. Adding regular expressions to graph reachability and pattern queries. In ICDE, pages 39--50, 2011. Google Scholar
Digital Library
- W. Fan, J. Li, S. Ma, N. Tang, and Y. Wu. Graph pattern matching: from intractable to polynomial time. PVLDB, 3(1):264--275, 2010. Google Scholar
Digital Library
- G. Fletcher et al. Relative expressive power of navigational querying on graphs. ICDT 2011, 197--207. Google Scholar
Digital Library
- G. Fletcher et al. The impact of transitive closure on the boolean expressiveness of navigational query languages on graphs. FoIKS 2012, 124--143. Google Scholar
Digital Library
- G. Gottlob and C. Koch. Monadic datalog and the expressive power of languages for web information extraction. J. ACM, 51(1):74--113, 2004. Google Scholar
Digital Library
- G. Gottlob, E. Grädel, and H. Veith. Datalog LITE: a deductive query language with linear time model checking. ACM TOCL, 3(1):42--79, 2002. Google Scholar
Digital Library
- D. Harel, D. Kozen, and J. Tiuryn. Dynamic Logic. MIT Press, 2000. Google Scholar
Digital Library
- S. Harris et al. SPARQL 1.1 Query Language. http://www.w3.org/TR/sparql11-query.Google Scholar
- N. Immerman, D. Kozen. Definability with Bounded Number of Bound Variables. IANDC, 83(2):121--139 (1989). Google Scholar
Digital Library
- The Apache Jena Manual. http://jena.apache.org.Google Scholar
- M. Kaminski and N. Francez. Finite memory automata. TCS, 134(2):329--363, 1994. Google Scholar
Digital Library
- L. Libkin. Elements of Finite Model Theory, Springer, 2004. Google Scholar
Digital Library
- L. Libkin, W. Martens, and D. Vrgoć. Querying graph databases with XPath. In ICDT, 2013. Google Scholar
Digital Library
- L. Libkin and D. Vrgoč. Regular path queries on graphs with data. In ICDT'12, pages 74--85. Google Scholar
Digital Library
- D. Leinders, M. Marx, J. Tyszkiewicz and J. Van den Bussche. The semijoin algebra and the guarded fragment. Logic, Language and Information, 14(3), 331--343, 2009. Google Scholar
Digital Library
- K. Losemann, W. Martens. The complexity of evaluating path expressions in SPARQL. In PODS'12, pages 101--112. Google Scholar
Digital Library
- The Neo4j Manual. http://docs.neo4j.org.Google Scholar
- J. Pérez, M. Arenas, and C. Gutierrez. Semantics and complexity of SPARQL. ACM TODS, 34(3), 2009. Google Scholar
Digital Library
- J. Pérez, M. Arenas, C. Gutierrez. nSPARQL: A navigational language for RDF. J. Web Sem., 8(4):255--270, 2010. Google Scholar
Digital Library
- E. Prud'hommeaux and A. Seaborne. SPARQL query language for RDF. W3C Recommendation 15 January 2008, http://www.w3.org/TR/rdf-sparql-query/.Google Scholar
- B. ten Cate. The expressivity of XPath with transitive closure. In PODS, pages 328--337, 2006. Google Scholar
Digital Library
- M. Vardi. On the complexity of bounded-variable queries. In PODS'95, pages 266--276. Google Scholar
Digital Library
- P. Wood. Query languages for graph databases. Sigmod Record, 41(1):50--60, 2012. Google Scholar
Digital Library
Index Terms
Trial for RDF: adapting graph query languages for RDF data
Recommendations
TriAL: A Navigational Algebra for RDF Triplestores
Best of SIGMOD 2016 Papers and Regular PapersNavigational queries over RDF data are viewed as one of the main applications of graph query languages, and yet the standard model of graph databases—essentially labeled graphs—is different from the triples-based model of RDF. While encodings of RDF ...
RDF, Jena, SparQL and the 'Semantic Web'
SIGUCCS '09: Proceedings of the 37th annual ACM SIGUCCS fall conference: communication and collaborationThe Resource Description Format (RDF) is used to represent information modeled as a "graph": a set of individual objects, along with a set of connections among those objects. In that role, RDF is one of the pillars of the so-called Semantic Web. This ...
The RDF foundry: call for an initiative to build enhanced RDF resources for biological data integration
WIMS '11: Proceedings of the International Conference on Web Intelligence, Mining and SemanticsCurrently, the OBO Foundry plays an important role by setting guidelines to formalise the concepts within the biomedical domain. The ontologies within the OBO Foundry are usually represented in the OBO ontology language. While being human-readable, this ...






Comments