More complicated questions about maxima and minima, and some closures of NP
Theoretical Computer Science
A very hard log-space counting class
Theoretical Computer Science - Special issue on structure in complexity theory
A taxonomy of complexity classes of functions
Journal of Computer and System Sciences
Finding Regular Simple Paths in Graph Databases
SIAM Journal on Computing
Rewriting of regular expressions and regular path queries
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
Jena: implementing the semantic web recommendations
Proceedings of the 13th international World Wide Web conference on Alternate track papers & posters
Efficient algorithms for processing XPath queries
ACM Transactions on Database Systems (TODS)
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2004
Extending SPARQL with regular expression patterns (for querying RDF)
Web Semantics: Science, Services and Agents on the World Wide Web
Semantics and complexity of SPARQL
ACM Transactions on Database Systems (TODS)
Executing SPARQL Queries over the Web of Linked Data
ISWC '09 Proceedings of the 8th International Semantic Web Conference
Expressive languages for path queries over graph-structured data
Proceedings of the twenty-ninth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
nSPARQL: A navigational language for RDF
Web Semantics: Science, Services and Agents on the World Wide Web
The KGRAM Abstract Machine for Knowledge Graph Querying
WI-IAT '10 Proceedings of the 2010 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology - Volume 01
The complexity of evaluating path expressions in SPARQL
PODS '12 Proceedings of the 31st symposium on Principles of Database Systems
Foundations of regular expressions in XML schema languages and SPARQL
PhD '12 Proceedings of the on SIGMOD/PODS 2012 PhD Symposium
How (well) do datalog, SPARQL and RIF interplay?
Datalog 2.0'12 Proceedings of the Second international conference on Datalog in Academia and Industry
SRBench: a streaming RDF/SPARQL benchmark
ISWC'12 Proceedings of the 11th international conference on The Semantic Web - Volume Part I
Using SPARQL to query bioportal ontologies and metadata
ISWC'12 Proceedings of the 11th international conference on The Semantic Web - Volume Part II
Querying Semantic Data on the Web?
ACM SIGMOD Record
Walk logic as a framework for path query languages on graph databases
Proceedings of the 16th International Conference on Database Theory
From DBpedia to Wikipedia: Filling the Gap by Discovering Wikipedia Conventions
WI-IAT '12 Proceedings of the The 2012 IEEE/WIC/ACM International Joint Conferences on Web Intelligence and Intelligent Agent Technology - Volume 01
BlueFinder: recommending wikipedia links using DBpedia properties
Proceedings of the 5th Annual ACM Web Science Conference
Proceedings of the 32nd symposium on Principles of database systems
A trichotomy for regular simple path queries on graphs
Proceedings of the 32nd symposium on Principles of database systems
Sparqling kleene: fast property paths in RDF-3X
First International Workshop on Graph Data Management Experiences and Systems
Proceedings of the 22nd international conference on World Wide Web
The complexity of regular expressions and property paths in SPARQL
ACM Transactions on Database Systems (TODS) - Invited papers issue
Efficient separability of regular languages by subsequences and suffixes
ICALP'13 Proceedings of the 40th international conference on Automata, Languages, and Programming - Volume Part II
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SPARQL -the standard query language for querying RDF- provides only limited navigational functionalities, although these features are of fundamental importance for graph data formats such as RDF. This has led the W3C to include the property path feature in the upcoming version of the standard, SPARQL 1.1.We tested several implementations of SPARQL 1.1 handling property path queries, and we observed that their evaluation methods for this class of queries have a poor performance even in some very simple scenarios. To formally explain this fact, we conduct a theoretical study of the computational complexity of property paths evaluation. Our results imply that the poor performance of the tested implementations is not a problem of these particular systems, but of the specification itself. In fact, we show that any implementation that adheres to the SPARQL 1.1 specification (as of November 2011) is doomed to show the same behavior, the key issue being the need for counting solutions imposed by the current specification. We provide several intractability results, that together with our empirical results, provide strong evidence against the current semantics of SPARQL 1.1 property paths. Finally, we put our results in perspective, and propose a natural alternative semantics with tractable evaluation, that we think may lead to a wide adoption of the language by practitioners, developers and theoreticians.