Foundations of logic programming
Foundations of logic programming
Semantical considerations on nonmonotonic logic
Artificial Intelligence
Applications of circumscription to formalizing common-sense knowledge
Artificial Intelligence
Relational queries computable in polynomial time
Information and Control
A note on succinct representations of graphs
Information and Control
Principles of database and knowledge-base systems, Vol. I
Principles of database and knowledge-base systems, Vol. I
The complexity of optimization problems
Journal of Computer and System Sciences - Structure in Complexity Theory Conference, June 2-5, 1986
On the declarative semantics of deductive databases and logic programs
Foundations of deductive databases and logic programming
Generalized closed world assumption is II-complete
Information Processing Letters
Logic programming and databases
Logic programming and databases
General logical databases and programs: default logic semantics and stratification
Information and Computation
The expressive power of stratified logic programs
Information and Computation
Journal of Computer and System Sciences
Elements of relational database theory
Handbook of theoretical computer science (vol. B)
The well-founded semantics for general logic programs
Journal of the ACM (JACM)
Foundations of disjunctive logic programming
Foundations of disjunctive logic programming
PODS '93 Proceedings of the twelfth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Implementing semantics of disjunctive logic programs using fringes and abstract properties
Proceedings of the second international workshop on Logic programming and non-monotonic reasoning
Extended logic programs as autoepistemic theories
Proceedings of the second international workshop on Logic programming and non-monotonic reasoning
Minimal knowledge + negation as failure = only knowing (sometimes)
Proceedings of the second international workshop on Logic programming and non-monotonic reasoning
Relating disjunctive logic programs to default theories
Proceedings of the second international workshop on Logic programming and non-monotonic reasoning
The complexity of algorithmic problems on succinct instances
Computer science
Stable and extension class theory for logic programs and default logics
Journal of Automated Reasoning
Adding disjunction to datalog (extended abstract)
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Proceedings of the eleventh international conference on Logic programming
Mixed integer programming methods for computing nonmonotonic deductive databases
Journal of the ACM (JACM)
Modular stratification and magic sets for Datalog programs with negation
Journal of the ACM (JACM)
A knowledge representation framework based on autoepistemic logic of minimal beliefs
AAAI'94 Proceedings of the twelfth national conference on Artificial intelligence (vol. 2)
Computing circumscriptive databases, I: theory and algorithms
Information and Computation
Translating default logic into standard autoepistemic logic
Journal of the ACM (JACM)
Logical foundations of object-oriented and frame-based languages
Journal of the ACM (JACM)
The expressive powers of the logic programming semantics
Selected papers of the 9th annual ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
On the expressive power of Datalog: tools and a case study
Selected papers of the 9th annual ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Implementing deductive databases by mixed integer programming
ACM Transactions on Database Systems (TODS)
Querying disjunctive databases through nonmonotonic logics
Theoretical Computer Science
The expressive powers of stable models for bound and unbound DATALOG queries
Journal of Computer and System Sciences - special issue on complexity theory
Stable models and non-determinism in logic programs with negation
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Non-deterministic languages to express deterministic transformations
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
On the complexity of unique solutions
Journal of the ACM (JACM)
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
Description Logics in Data Management
IEEE Transactions on Knowledge and Data Engineering
Default Logic as a Query Language
IEEE Transactions on Knowledge and Data Engineering
Lanczos Algorithms for Large Symmetric Eigenvalue Computations, Vol. 1
Lanczos Algorithms for Large Symmetric Eigenvalue Computations, Vol. 1
Second Order Logic and the Weak Exponential Hierarchies
MFCS '95 Proceedings of the 20th International Symposium on Mathematical Foundations of Computer Science
On the Extension of Logic Programming with Negation through Uniform Proofs
LPNMR '95 Proceedings of the Third International Conference on Logic Programming and Nonmonotonic Reasoning
Reasoning with Stratified Default Theories
LPNMR '95 Proceedings of the Third International Conference on Logic Programming and Nonmonotonic Reasoning
A Restricted Second Order Logic for Finite Structures
LCC '94 Selected Papers from the International Workshop on Logical and Computational Complexity
The Expressive Power of Partial Models in Disjunctive Deductive Databases
LID '96 Proceedings of the International Workshop on Logic in Databases
On Indefinite Databases and the Closed World Assumption
Proceedings of the 6th Conference on Automated Deduction
Succinct Representation, Leaf Languages, and Projection Reductions
CCC '96 Proceedings of the 11th Annual IEEE Conference on Computational Complexity
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
Complexity and expressive power of logic programming
ACM Computing Surveys (CSUR)
Description logics of minimal knowledge and negation as failure
ACM Transactions on Computational Logic (TOCL)
An Extension to GCWA and Query Evaluation for Disjunctive Deductive Databases
Journal of Intelligent Information Systems
Declarative problem-solving using the DLV system
Logic-based artificial intelligence
Logic-based artificial intelligence
Logic programming and knowledge representation-the A-prolog perspective
Artificial Intelligence
Extending and implementing the stable model semantics
Artificial Intelligence
Semantics and expressiveness of disjunctive ordered logic
Annals of Mathematics and Artificial Intelligence
On the complexity of data disjunctions
Theoretical Computer Science - Complexity and logic
Enhancing Disjunctive Datalog by Constraints
IEEE Transactions on Knowledge and Data Engineering
A Deductive Database Approach to A.I. Planning
Journal of Intelligent Information Systems
Conflict Resolution Using Logic Programming
IEEE Transactions on Knowledge and Data Engineering
Binding Propagation Techniques for the Optimization of Bound Disjunctive Queries
IEEE Transactions on Knowledge and Data Engineering
A Logic Programming Approach to the Integration, Repairing and Querying of Inconsistent Databases
Proceedings of the 17th International Conference on Logic Programming
On Reasoning about Structural Equality in XML: A Description Logic Approach
ICDT '03 Proceedings of the 9th International Conference on Database Theory
Query Optimization of Disjunctive Databases with Constraints through Binding Propagation
LPAR '02 Proceedings of the 9th International Conference on Logic for Programming, Artificial Intelligence, and Reasoning
Binding Propagation in Disjunctive Databases
VLDB '98 Proceedings of the 24rd International Conference on Very Large Data Bases
Multiagent Compromises, Joint Fixpoints, and Stable Models
Computational Logic: Logic Programming and Beyond, Essays in Honour of Robert A. Kowalski, Part I
Fixed-Parameter Complexity in AI and Nonmonotonic Reasoning
LPNMR '99 Proceedings of the 5th International Conference on Logic Programming and Nonmonotonic Reasoning
Minimal Founded Semantics for Disjunctive Logic Programming
LPNMR '99 Proceedings of the 5th International Conference on Logic Programming and Nonmonotonic Reasoning
Improving ASP Instantiators by Join-Ordering Methods
LPNMR '01 Proceedings of the 6th International Conference on Logic Programming and Nonmonotonic Reasoning
Extending Disjunctive Logic Programming by T-norms
LPNMR '99 Proceedings of the 5th International Conference on Logic Programming and Nonmonotonic Reasoning
Generalized Quantifiers in Logic Programs
ESSLLI '97 Revised Lectures from the 9th European Summer School on Logic, Language, and Information: Generalized Quantifiers and Computation
On Complexity of Updates through Integrity Constraints
CL '00 Proceedings of the First International Conference on Computational Logic
Local Search Techniques for Disjunctive Logic Programs
AI*IA '99 Proceedings of the 6th Congress of the Italian Association for Artificial Intelligence on Advances in Artificial Intelligence
Abduction with Penalization in Logic Programming
AI*IA 01 Proceedings of the 7th Congress of the Italian Association for Artificial Intelligence on Advances in Artificial Intelligence
A technique for information system integration
ISTA '01 Proceedings of the 2001 international conference on Information systems technology and its applications - Volume P-2
Consistent queries over databases with integrity constraints
Database integrity
Nonmonotonic reasoning: towards efficient calculi and implementations
Handbook of automated reasoning
Complexity and Expressive Power of Logic Programming
CCC '97 Proceedings of the 12th Annual IEEE Conference on Computational Complexity
On the rewriting and efficient computation of bound disjunctive datalog queries
Proceedings of the 5th ACM SIGPLAN international conference on Principles and practice of declaritive programming
Repairing and querying inconsistent databases
Effective databases for text & document management
A Logical Framework for Querying and Repairing Inconsistent Databases
IEEE Transactions on Knowledge and Data Engineering
Enhancing disjunctive logic programming systems by SAT checkers
Artificial Intelligence
Optimal Models of Disjunctive Logic Programs: Semantics, Complexity, and Computation
IEEE Transactions on Knowledge and Data Engineering
An abductive framework for computing knowledge base updates
Theory and Practice of Logic Programming
Minimal founded semantics for disjunctive logic programs and deductive databases
Theory and Practice of Logic Programming
Disjunctive logic programs with inheritance
Theory and Practice of Logic Programming
A logic-based approach to data integration
Theory and Practice of Logic Programming
On properties of update sequences based on causal rejection
Theory and Practice of Logic Programming
Reasoning with infinite stable models
Artificial Intelligence
PPDP '04 Proceedings of the 6th ACM SIGPLAN international conference on Principles and practice of declarative programming
Abductive logic programs with penalization: semantics, complexity and implementation
Theory and Practice of Logic Programming
Encyclopedia of Computer Science
Optimization of bound disjunctive queries with constraints
Theory and Practice of Logic Programming
Consistent query answering under key and exclusion dependencies: algorithms and experiments
Proceedings of the 14th ACM international conference on Information and knowledge management
Theory and Practice of Logic Programming
Unfolding partiality and disjunctions in stable model semantics
ACM Transactions on Computational Logic (TOCL)
Position paper: a comparison of two modelling paradigms in the Semantic Web
Proceedings of the 15th international conference on World Wide Web
The DLV system for knowledge representation and reasoning
ACM Transactions on Computational Logic (TOCL)
Exploiting agents in e-learning and skills management context
AI Communications
A backjumping technique for disjunctive logic programming
AI Communications
Splitting an operator: Algebraic modularity results for logics with fixpoint semantics
ACM Transactions on Computational Logic (TOCL)
The Diagnosis Frontend of the dlv system
AI Communications
Quantitative Disjunctive Logic Programming: semantics and computation
AI Communications
Parametric connectives in Disjunctive Logic Programming
AI Communications
Pruning Operators for Disjunctive Logic Programming Systems
Fundamenta Informaticae
A knowledge-based approach for selecting information sources
Theory and Practice of Logic Programming
Magic Sets and their application to data integration
Journal of Computer and System Sciences
Semantical characterizations and complexity of equivalences in answer set programming
ACM Transactions on Computational Logic (TOCL)
A framework for prioritized reasoning based on the choice evaluation
Proceedings of the 2007 ACM symposium on Applied computing
Semantic extraction and adaptive delivery of multimedia contents for the cultural assets
Proceedings of the second workshop on Use of P2P, GRID and agents for the development of content networks
Solving abduction by computing joint explanations
Annals of Mathematics and Artificial Intelligence
Reasoning in Description Logics by a Reduction to Disjunctive Datalog
Journal of Automated Reasoning
A comparison of two modelling paradigms in the Semantic Web
Web Semantics: Science, Services and Agents on the World Wide Web
On look-ahead heuristics in disjunctive logic programming
Annals of Mathematics and Artificial Intelligence
Complexity results for answer set programming with bounded predicate arities and implications
Annals of Mathematics and Artificial Intelligence
Repair localization for query answering from inconsistent databases
ACM Transactions on Database Systems (TODS)
Computing minimum cost diagnoses to repair populated DL-based ontologies
Proceedings of the 17th international conference on World Wide Web
Authorization in trust management: Features and foundations
ACM Computing Surveys (CSUR)
Experimenting with parallelism for the instantiation of ASP programs
Journal of Algorithms
Modeling and Analyzing Variability for Mobile Information Systems
ICCSA '08 Proceedings of the international conference on Computational Science and Its Applications, Part II
Foundations of Onto-Relational Learning
ILP '08 Proceedings of the 18th international conference on Inductive Logic Programming
JELIA '08 Proceedings of the 11th European conference on Logics in Artificial Intelligence
On Combining Description Logic Ontologies and Nonrecursive Datalog Rules
RR '08 Proceedings of the 2nd International Conference on Web Reasoning and Rule Systems
Lexicographical Inference over Inconsistent DL-Based Ontologies
RR '08 Proceedings of the 2nd International Conference on Web Reasoning and Rule Systems
Modeling and analysis of procedural security in (e)voting: the Trentino's approach and experiences
EVT'08 Proceedings of the conference on Electronic voting technology
Computing Only Minimal Answers in Disjunctive Deductive Databases
Journal of Automated Reasoning
The DLV Project: A Tour from Theory and Research to Applications and Market
ICLP '08 Proceedings of the 24th International Conference on Logic Programming
Composing Normal Programs with Function Symbols
ICLP '08 Proceedings of the 24th International Conference on Logic Programming
Design and implementation of aggregate functions in the dlv system*
Theory and Practice of Logic Programming
Logic programming with social features1
Theory and Practice of Logic Programming
Achieving compositionality of the stable model semantics for smodels programs1
Theory and Practice of Logic Programming
Stable models and difference logic
Annals of Mathematics and Artificial Intelligence
Bridging the gap between OWL and relational databases
Web Semantics: Science, Services and Agents on the World Wide Web
Resource allocation with answer-set programming
Proceedings of The 8th International Conference on Autonomous Agents and Multiagent Systems - Volume 1
Modular Equivalence for Normal Logic Programs
Proceedings of the 2006 conference on ECAI 2006: 17th European Conference on Artificial Intelligence August 29 -- September 1, 2006, Riva del Garda, Italy
An Architecture for Requirements-Driven Self-reconfiguration
CAiSE '09 Proceedings of the 21st International Conference on Advanced Information Systems Engineering
Complexity of the Stable Model Semantics for Queries on Incomplete Databases
LPNMR '09 Proceedings of the 10th International Conference on Logic Programming and Nonmonotonic Reasoning
An ASP-Based System for e-Tourism
LPNMR '09 Proceedings of the 10th International Conference on Logic Programming and Nonmonotonic Reasoning
Some DLV Applications for Knowledge Management
LPNMR '09 Proceedings of the 10th International Conference on Logic Programming and Nonmonotonic Reasoning
Designing, Specifying and Querying Metadata for Virtual Data Integration Systems
Globe '09 Proceedings of the 2nd International Conference on Data Management in Grid and Peer-to-Peer Systems
Magic sets for data integration
AAAI'08 Proceedings of the 23rd national conference on Artificial intelligence - Volume 3
On the semantics of logic programs with preferences
Journal of Artificial Intelligence Research
Stable model checking made easy
IJCAI'99 Proceedings of the 16th international joint conference on Artifical intelligence - Volume 1
Characterising equilibrium logic and nested logic programs: Reductions and complexity1,2
Theory and Practice of Logic Programming
Efficient description logic reasoning in prolog: The dlog system
Theory and Practice of Logic Programming
The complexity of circumscription in description logic
Journal of Artificial Intelligence Research
Modularity aspects of disjunctive stable models
Journal of Artificial Intelligence Research
Experimenting with heuristics for answer set programming
IJCAI'01 Proceedings of the 17th international joint conference on Artificial intelligence - Volume 1
Heuristics for hard ASP programs
IJCAI'05 Proceedings of the 19th international joint conference on Artificial intelligence
FDNC: Decidable nonmonotonic disjunctive logic programs with function symbols
ACM Transactions on Computational Logic (TOCL)
Answer Sets in a Fuzzy Equilibrium Logic
RR '09 Proceedings of the 3rd International Conference on Web Reasoning and Rule Systems
A parallel ASP instantiator based on DLV
Proceedings of the 5th ACM SIGPLAN workshop on Declarative aspects of multicore programming
Fundamenta Informaticae - Advances in Computational Logic (CIL C08)
Query Answering for OWL-DL with rules
Web Semantics: Science, Services and Agents on the World Wide Web
On the decidability and complexity of integrating ontologies and rules
Web Semantics: Science, Services and Agents on the World Wide Web
Reconciling description logics and rules
Journal of the ACM (JACM)
On the complexity of answer set programming with aggregates
LPNMR'07 Proceedings of the 9th international conference on Logic programming and nonmonotonic reasoning
Experimenting with look-back heuristics for hard ASP programs
LPNMR'07 Proceedings of the 9th international conference on Logic programming and nonmonotonic reasoning
Modularity aspects of disjunctive stable models
LPNMR'07 Proceedings of the 9th international conference on Logic programming and nonmonotonic reasoning
Modularity in SMODELS programs
LPNMR'07 Proceedings of the 9th international conference on Logic programming and nonmonotonic reasoning
Hierarchical decision making in multi-agent systems using answer set programming
CLIMA VII'06 Proceedings of the 7th international conference on Computational logic in multi-agent systems
Querying inconsistent databases
LPAR'00 Proceedings of the 7th international conference on Logic for programming and automated reasoning
The consistency extractor system: Answer set programs for consistent query answering in databases
Data & Knowledge Engineering
Prioritized active integrity constraints for database maintenance
DASFAA'07 Proceedings of the 12th international conference on Database systems for advanced applications
Pure, declarative, and constructive arithmetic relations (declarative pearl)
FLOPS'08 Proceedings of the 9th international conference on Functional and logic programming
Theory and Practice of Logic Programming
Inductive logic programming in databases: From datalog to $\mathcal{dl}+log}^{\neg\vee}$
Theory and Practice of Logic Programming
Catching the ouroboros: On debugging non-ground answer-set programs
Theory and Practice of Logic Programming
A 25-year perspective on logic programming
Logic programming languages for databases and the web
A 25-year perspective on logic programming
Hybrid reasoning with non-monotonic rules
ReasoningWeb'10 Proceedings of the 6th international conference on Semantic technologies for software engineering
Nonmonotonic onto-relational learning
ILP'09 Proceedings of the 19th international conference on Inductive logic programming
Semantics and complexity of recursive aggregates in answer set programming
Artificial Intelligence
ASP at work: spin-off and applications of the DLV system
Logic programming, knowledge representation, and nonmonotonic reasoning
On the practical side of answer set programming
Logic programming, knowledge representation, and nonmonotonic reasoning
Dynamic magic sets for programs with monotone recursive aggregates
LPNMR'11 Proceedings of the 11th international conference on Logic programming and nonmonotonic reasoning
ASPIDE: integrated development environment for answer set programming
LPNMR'11 Proceedings of the 11th international conference on Logic programming and nonmonotonic reasoning
The third answer set programming competition: preliminary report of the system competition track
LPNMR'11 Proceedings of the 11th international conference on Logic programming and nonmonotonic reasoning
Conjunctive query answering in the description logic SH using knots
Journal of Computer and System Sciences
Data integration and answer set programming
LPNMR'05 Proceedings of the 8th international conference on Logic Programming and Nonmonotonic Reasoning
Solving hard ASP programs efficiently
LPNMR'05 Proceedings of the 8th international conference on Logic Programming and Nonmonotonic Reasoning
Answer set programming: a declarative approach to solving search problems
JELIA'06 Proceedings of the 10th European conference on Logics in Artificial Intelligence
On the semantics of logic programs with preferences
JELIA'06 Proceedings of the 10th European conference on Logics in Artificial Intelligence
Ordered completion for first-order logic programs on finite structures
Artificial Intelligence
Declarative semantics of production rules for integrity maintenance
ICLP'06 Proceedings of the 22nd international conference on Logic Programming
Efficient application of answer set programming for advanced data integration
PADL'10 Proceedings of the 12th international conference on Practical Aspects of Declarative Languages
Magic sets and their application to data integration
ICDT'05 Proceedings of the 10th international conference on Database Theory
Aggregates and preferences in logic programming
ISMIS'05 Proceedings of the 15th international conference on Foundations of Intelligent Systems
Semantic and computational advantages of the safe integration of ontologies and rules
PPSWR'05 Proceedings of the Third international conference on Principles and Practice of Semantic Web Reasoning
DALT'09 Proceedings of the 7th international conference on Declarative Agent Languages and Technologies
First-Order encodings for modular nonmonotonic datalog programs
Datalog'10 Proceedings of the First international conference on Datalog Reloaded
Equivalence between extended datalog programs -- a brief survey
Datalog'10 Proceedings of the First international conference on Datalog Reloaded
Unfounded sets and well-founded semantics of answer set programs with aggregates
Journal of Artificial Intelligence Research
Magic Sets for disjunctive Datalog programs
Artificial Intelligence
On the complexity of query answering over incomplete XML documents
Proceedings of the 15th International Conference on Database Theory
Translating first-order theories into logic programs
IJCAI'11 Proceedings of the Twenty-Second international joint conference on Artificial Intelligence - Volume Volume Two
Fuzzy Equilibrium Logic: Declarative Problem Solving in Continuous Domains
ACM Transactions on Computational Logic (TOCL)
Parameterized splitting: a simple modification-based approach
Correct Reasoning
The intelligent grounder of DLV
Correct Reasoning
Aligning software configuration with business and IT context
CAiSE'12 Proceedings of the 24th international conference on Advanced Information Systems Engineering
Fundamenta Informaticae - Advances in Computational Logic (CIL C08)
On the complexity of ontological reasoning under disjunctive existential rules
MFCS'12 Proceedings of the 37th international conference on Mathematical Foundations of Computer Science
Pruning Operators for Disjunctive Logic Programming Systems
Fundamenta Informaticae
Reasoning with contextual requirements: Detecting inconsistency and conflicts
Information and Software Technology
Foundations of rule-based query answering
RW'07 Proceedings of the Third international summer school conference on Reasoning Web
RW'07 Proceedings of the Third international summer school conference on Reasoning Web
The multi-engine ASP solver ME-ASP
JELIA'12 Proceedings of the 13th European conference on Logics in Artificial Intelligence
A PROV encoding for provenance analysis using deductive rules
IPAW'12 Proceedings of the 4th international conference on Provenance and Annotation of Data and Processes
Datalog 2.0'12 Proceedings of the Second international conference on Datalog in Academia and Industry
Disjunctive datalog with existential quantifiers: Semantics, decidability, and complexity issues
Theory and Practice of Logic Programming
Modeling and solving technical product configuration problems
Artificial Intelligence for Engineering Design, Analysis and Manufacturing
Towards Practical ABox Abduction in Large Description Logic Ontologies
International Journal on Semantic Web & Information Systems
Advanced computational reasoning based on the NKRL conceptual model
Expert Systems with Applications: An International Journal
Ontology-based data access: a study through disjunctive datalog, CSP, and MMSNP
Proceedings of the 32nd symposium on Principles of database systems
Answer set programming: language, applications and development tools
RR'13 Proceedings of the 7th international conference on Web Reasoning and Rule Systems
Modeling stable matching problems with answer set programming
RuleML'13 Proceedings of the 7th international conference on Theory, Practice, and Applications of Rules on the Web
The impact of disjunction on query answering under guarded-based existential rules
IJCAI'13 Proceedings of the Twenty-Third international joint conference on Artificial Intelligence
First-order expressibility and boundedness of disjunctive logic programs
IJCAI'13 Proceedings of the Twenty-Third international joint conference on Artificial Intelligence
Synthesizing Concurrent Programs Using Answer Set Programming
Fundamenta Informaticae - Concurrency Specification and Programming CS&P
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We consider disjunctive Datalog, a powerful database query language based on disjunctive logic programming. Briefly, disjunctive Datalog is a variant of Datalog where disjunctions may appear in the rule heads; advanced versions also allow for negation in the bodies which can be handled according to a semantics for negation in disjunctive logic programming. In particular, we investigate three different semantics for disjunctive Datalog: the minimal model semantics the perfect model semantics, and the stable model semantics. For each of these semantics, the expressive power and complexity are studied. We show that the possibility variants of these semantics express the same set of queries. In fact, they precisely capture the complexity class P2 . Thus, unless the Polynomial Hierarchy collapses, disjunctive Datalog is more expressive that normal logic programming with negation. These results are not only of theoretical interest; we demonstrate that problems relevant in practice such as computing the optimal tour value in the Traveling Salesman Problem and eigenvector computations can be handled in disjunctive Datalog, but not Datalog with negation (unless the Polynomial Hierarchy collapses). In addition, we study modularity properties of disjunctive Datalog and investigate syntactic restrictions of the formalisms.