A graphical query language supporting recursion
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
Definability with bounded number of bound variables
Information and Computation
Theoretical Computer Science
On the complexity of bounded-variable queries (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
GraphLog: a visual formalism for real life recursion
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Datalog LITE: a deductive query language with linear time model checking
ACM Transactions on Computational Logic (TOCL)
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
Dynamic Logic
Ρ-Queries: enabling querying for semantic associations on the semantic web
WWW '03 Proceedings of the 12th international conference on World Wide Web
Monadic datalog and the expressive power of languages for Web information extraction
Journal of the ACM (JACM)
Elements Of Finite Model Theory (Texts in Theoretical Computer Science. An Eatcs Series)
Elements Of Finite Model Theory (Texts in Theoretical Computer Science. An Eatcs Series)
The Semijoin Algebra and the Guarded Fragment
Journal of Logic, Language and Information
The expressivity of XPath with transitive closure
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Survey of graph database models
ACM Computing Surveys (CSUR)
Semantics and complexity of SPARQL
ACM Transactions on Database Systems (TODS)
nSPARQL: A navigational language for RDF
Web Semantics: Science, Services and Agents on the World Wide Web
Graph pattern matching: from intractable to polynomial time
Proceedings of the VLDB Endowment
Relative expressive power of navigational querying on graphs
Proceedings of the 14th International Conference on Database Theory
Querying semantic web data with SPARQL
Proceedings of the thirtieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Adding regular expressions to graph reachability and pattern queries
ICDE '11 Proceedings of the 2011 IEEE 27th International Conference on Data Engineering
Query languages for graph databases
ACM SIGMOD Record
The complexity of evaluating path expressions in SPARQL
PODS '12 Proceedings of the 31st symposium on Principles of Database Systems
FoIKS'12 Proceedings of the 7th international conference on Foundations of Information and Knowledge Systems
Regular path queries on graphs with data
Proceedings of the 15th International Conference on Database Theory
Graph Logics with Rational Relations and the Generalized Intersection Problem
LICS '12 Proceedings of the 2012 27th Annual IEEE/ACM Symposium on Logic in Computer Science
A Comparison of Current Graph Database Models
ICDEW '12 Proceedings of the 2012 IEEE 28th International Conference on Data Engineering Workshops
Expressive Languages for Path Queries over Graph-Structured Data
ACM Transactions on Database Systems (TODS)
Querying graph databases with XPath
Proceedings of the 16th International Conference on Database Theory
Schema mappings and data exchange for graph databases
Proceedings of the 16th International Conference on Database Theory
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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.