A graphical query language supporting recursion
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
A very hard log-space counting class
Theoretical Computer Science - Special issue on structure in complexity theory
A linear-time model-checking algorithm for the alternation-free modal mu-calculus
Formal Methods in System Design - Special issue on computer-aided verification: special methods II
Finding Regular Simple Paths in Graph Databases
SIAM Journal on Computing
A query language and optimization techniques for unstructured data
SIGMOD '96 Proceedings of the 1996 ACM SIGMOD international conference on Management of data
Query containment for conjunctive queries with regular expressions
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
One-unambiguous regular languages
Information and Computation
Graph-theoretic methods in database theory
PODS '90 Proceedings of the ninth 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
Counting and random generation of strings in regular languages
Proceedings of the sixth annual ACM-SIAM symposium on Discrete algorithms
Regular path queries with constraints
Journal of Computer and System Sciences
View-based query processing for regular path queries with inverse
PODS '00 Proceedings of the nineteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Database Management Systems
Introduction To Automata Theory, Languages, And Computation
Introduction To Automata Theory, Languages, And Computation
MPC '02 Proceedings of the 6th International Conference on Mathematics of Program Construction
Optimization Properties for Classes of Conjunctive Regular Path Queries
DBPL '01 Revised Papers from the 8th International Workshop on Database Programming Languages
Declarative specification of Web sites with S
The VLDB Journal — The International Journal on Very Large Data Bases
One-unambiguity of regular expressions with numeric occurrence indicators
Information and Computation
Ambiguity in Graphs and Expressions
IEEE Transactions on Computers
Efficient asymmetric inclusion between regular expression types
Proceedings of the 12th International Conference on Database Theory
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)
Efficient inclusion for a class of XML types with interleaving and counting
Information Systems
Optimizing Schema Languages for XML: Numerical Constraints and Interleaving
SIAM Journal on Computing
Inference of concise regular expressions and DTDs
ACM Transactions on Database Systems (TODS)
Foundations of SPARQL query optimization
Proceedings of the 13th International Conference on Database Theory
nSPARQL: A navigational language for RDF
Web Semantics: Science, Services and Agents on the World Wide Web
Complexity of Decision Problems for XML Schemas and Chain Regular Expressions
SIAM Journal on Computing
Querying semantic web data with SPARQL
Proceedings of the thirtieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Counting beyond a Yottabyte, or how SPARQL 1.1 property paths will prevent adoption of the standard
Proceedings of the 21st international conference on World Wide Web
The complexity of evaluating path expressions in SPARQL
PODS '12 Proceedings of the 31st symposium on Principles of Database Systems
Regular path queries on graphs with data
Proceedings of the 15th International Conference on Database Theory
Regular Expressions with Counting: Weak versus Strong Determinism
SIAM Journal on Computing
Querying graph databases with XPath
Proceedings of the 16th International Conference on Database Theory
A trichotomy for regular simple path queries on graphs
Proceedings of the 32nd symposium on Principles of database systems
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The World Wide Web Consortium (W3C) recently introduced property paths in SPARQL 1.1, a query language for RDF data. Property paths allow SPARQL queries to evaluate regular expressions over graph-structured data. However, they differ from standard regular expressions in several notable aspects. For example, they have a limited form of negation, they have numerical occurrence indicators as syntactic sugar, and their semantics on graphs is defined in a nonstandard manner. We formalize the W3C semantics of property paths and investigate various query evaluation problems on graphs. More specifically, let x and y be two nodes in an edge-labeled graph and r be an expression. We study the complexities of: (1) deciding whether there exists a path from x to y that matches r and (2) counting how many paths from x to y match r. Our main results show that, compared to an alternative semantics of regular expressions on graphs, the complexity of (1) and (2) under W3C semantics is significantly higher. Whereas the alternative semantics remains in polynomial time for large fragments of expressions, the W3C semantics makes problems (1) and (2) intractable almost immediately. As a side-result, we prove that the membership problem for regular expressions with numerical occurrence indicators and negation is in polynomial time.