A Proof Procedure for Data Dependencies
Journal of the ACM (JACM)
The Two-Variable Guarded Fragment with Transitive Relations
LICS '99 Proceedings of the 14th Annual IEEE Symposium on Logic in Computer Science
Robbers, marshals, and guards: game theoretic and logical characterizations of hypertree width
Journal of Computer and System Sciences - Special issu on PODS 2001
On the Decision Problem for the Guarded Fragment with Transitivity
LICS '01 Proceedings of the 16th Annual IEEE Symposium on Logic in Computer Science
Complexity of the Two-Variable Fragment with Counting Quantifiers
Journal of Logic, Language and Information
Tractable Reasoning and Efficient Query Answering in Description Logics: The DL-Lite Family
Journal of Automated Reasoning
Data-complexity of the two-variable fragment with counting quantifiers
Information and Computation
The two-variable guarded fragment with transitive guards is 2EXPTIME-hard
FOSSACS'03/ETAPS'03 Proceedings of the 6th International conference on Foundations of Software Science and Computation Structures and joint European conference on Theory and practice of software
LICS '10 Proceedings of the 2010 25th Annual IEEE Symposium on Logic in Computer Science
ICALP'11 Proceedings of the 38th international conference on Automata, languages and programming - Volume Part II
Results on the guarded fragment with equivalence or transitive relations
CSL'05 Proceedings of the 19th international conference on Computer Science Logic
Walking the complexity lines for generalized guarded existential rules
IJCAI'11 Proceedings of the Twenty-Second international joint conference on Artificial Intelligence - Volume Volume Two
Extending decidable existential rules by joining acyclicity and guardedness
IJCAI'11 Proceedings of the Twenty-Second international joint conference on Artificial Intelligence - Volume Volume Two
On the complexity of ontological reasoning under disjunctive existential rules
MFCS'12 Proceedings of the 37th international conference on Mathematical Foundations of Computer Science
Data complexity of query answering in description logics
Artificial Intelligence
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We study the problem of answering a union of Boolean conjunctive queries q against a database Δ, and a logical theory ϕ which falls in the guarded fragment with transitive guards (GF + TG). We trace the frontier between decidability and undecidability of the problem under consideration. Surprisingly, we show that query answering under GF2 + TG, i.e., the two-variable fragment of GF + TG, is already undecidable (even without equality), whereas its monadic fragment is decidable; in fact, it is 2exptime-complete in combined complexity and coNP-complete in data complexity. We also show that for a restricted class of queries, query answering under GF+TG is decidable.