We give an algebraic specification that selects, among all solutions to the data exchange problem, a special class of solutions that we call universal.Expand

We give an algebraic specification that selects, among all solutions to the data exchange problem, a special class of solutions that we call universal.Expand

We give a rigorous semantics to the composition of schema mappings in which the specification is given by a finite set of source-to-target tuple-generating dependencies and investigate the definability and computational complexity of the composition.Expand

Data exchange is the problem of taking data structured under a source schema and creating an instance of a target schema that reflects the source data as accurately as possible.Expand

We show that several cases of tractable nonuniform constraint-satisfaction problems do indeed uniformize and give rise to polynomial-time solvable cases of constraint satisfaction and conjunctive-query containment.Expand

We improve Mortimer's bound by one exponential and show that every satisfiable FO2-sentence has a model whose size is at most exponential in the size of the sentence.Expand

In this paper, we give a polynomial-time algorithm for subset-repair checking under integrity constraints that are the union of a weakly acyclic set of local-as-view (LAV) tuple-generating dependencies and a set of equality-generative dependencies.Expand

We investigate the infinitary logic L∞ωω, in which sentences may have arbitrary disjunctions and conjunctions, but they involve only finite numbers of distinct variables.Expand