On the complexity of H-coloring
Journal of Combinatorial Theory Series B
Discrete Applied Mathematics
The complexity of iterated multiplication
Information and Computation
Completeness of path-problems via logical reductions
Information and Computation
Conjunctive-query containment and constraint satisfaction
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
List homomorphisms to reflexive graphs
Journal of Combinatorial Theory Series B
The complexity of counting graph homomorphisms
Proceedings of the ninth international conference on on Random structures and algorithms
Computers and Intractability: A Guide to the Theory of NP-Completeness
Computers and Intractability: A Guide to the Theory of NP-Completeness
Classification of Homomorphisms to Oriented Cycles and of k-Partite Satisfiability
SIAM Journal on Discrete Mathematics
Constraints and universal algebra
Annals of Mathematics and Artificial Intelligence
Descriptive Complexity and Model Checking
Proceedings of the 18th Conference on Foundations of Software Technology and Theoretical Computer Science
A Generic Greedy Algorithm, Partially-Ordered Graphs and NP-Completeness
WG '01 Proceedings of the 27th International Workshop on Graph-Theoretic Concepts in Computer Science
The Complexity of Restrictive H-Coloring
WG '02 Revised Papers from the 28th International Workshop on Graph-Theoretic Concepts in Computer Science
Greedy algorithms, H-colourings and a complexity-theoretic dichotomy
Theoretical Computer Science
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
The complexity of satisfiability problems
STOC '78 Proceedings of the tenth annual ACM symposium on Theory of computing
Bi-arc graphs and the complexity of list homomorphisms
Journal of Graph Theory
An Algebraic Framework for Schema Matching
Informatica
An algebraic framework for schema matching
WAIM'05 Proceedings of the 6th international conference on Advances in Web-Age Information Management
The dichotomy of list homomorphisms for digraphs
Proceedings of the twenty-second annual ACM-SIAM symposium on Discrete Algorithms
Survey: Colouring, constraint satisfaction, and complexity
Computer Science Review
Ontology-based data access: a study through disjunctive datalog, CSP, and MMSNP
Proceedings of the 32nd symposium on Principles of database systems
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We study non-uniform constraint satisfaction problems where the underlying signature contains constant and function symbols as well as relation symbols. Amongst our results are the following. We establish a dichotomy result for the class of non-uniform constraint satisfaction problems over the signature consisting of one unary function symbol by showing that every such problem is either complete for L, via very restricted logical reductions, or trivial (depending upon whether the template function has a fixed point or not). We show that the class of non-uniform constraint satisfaction problems whose templates are structures over the signature λ2 consisting of two unary function symbols reflects the full computational significance of the class of non-uniform constraint satisfaction problems over relational structures. We prove a dichotomy result for the class of non-uniform constraint satisfaction problems where the template is a λ2-structure with the property that the two unary functions involved are the reverse of one another, in that every such problem is either solvable in polynomial-time or NP-complete. Finally, we extend some of our results to the situation where instances of non-uniform constraint satisfaction problems come equipped with lists of elements of the template structure which restrict the set of allowable homomorphisms.