Three partition refinement algorithms
SIAM Journal on Computing
Database techniques for the World-Wide Web: a survey
ACM SIGMOD Record
Data on the Web: from relations to semistructured data and XML
Data on the Web: from relations to semistructured data and XML
Modal logic
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
Dynamic Logic
Structural Properties of XPath Fragments
ICDT '03 Proceedings of the 9th International Conference on Database Theory
Optimization Properties for Classes of Conjunctive Regular Path Queries
DBPL '01 Revised Papers from the 8th International Workshop on Database Programming Languages
Efficient processing of joins on set-valued attributes
Proceedings of the 2003 ACM SIGMOD international conference on Management of data
Semantic characterizations of navigational XPath
ACM SIGMOD Record
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2004
Forward node-selecting queries over trees
ACM Transactions on Database Systems (TODS)
The Description Logic Handbook
The Description Logic Handbook
Survey of graph database models
ACM Computing Surveys (CSUR)
A Study of a Positive Fragment of Path Queries
The Computer Journal
Query languages for graph databases
ACM SIGMOD Record
FoIKS'12 Proceedings of the 7th international conference on Foundations of Information and Knowledge Systems
Querying graph databases with XPath
Proceedings of the 16th International Conference on Database Theory
Definability problems for graph query languages
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
What we talk about when we talk about graphs
Proceedings of the Joint EDBT/ICDT 2013 Workshops
Semantic acyclicity on graph databases
Proceedings of the 32nd symposium on Principles of database systems
Proceedings of the 32nd symposium on Principles of database systems
Trial for RDF: adapting graph query languages for RDF data
Proceedings of the 32nd symposium on Principles of database systems
Learning queries for relational, semi-structured, and graph databases
Proceedings of the 2013 Sigmod/PODS Ph.D. symposium on PhD symposium
Proceedings of the 22nd international conference on World Wide Web
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Motivated by both established and new applications, we study navigational query languages for graphs (binary relations). The simplest language has only the two operators union and composition, together with the identity relation. We make more powerful languages by adding any of the following operators: intersection; set difference; projection; coprojection; converse; transitive closure; and the diversity relation. All these operators map binary relations to binary relations. We compare the expressive power of all resulting languages. We do this not only for general path queries (queries where the result may be any binary relation) but also for boolean or yes/no queries (expressed by the nonemptiness of an expression). For both cases, we present the complete Hasse diagram of relative expressiveness. In particular, the Hasse diagram for boolean queries contains nontrivial separations and a few surprising collapses.