A universal model of a database D and a set Σ of integrity constraints is a database that extends D, satisfies Σ, and is most general in the sense that it contains sound and co...
The problems of query containment, equivalence, and minimization are recognized as very important in the context of query processing, specifically of query optimization. In their...
We introduce a new normal form, called essential tuple normal form (ETNF), for relations in a relational database where the constraints are given by functional dependencies and jo...
In a recent paper by Hellerstein [15], a tight relationship was conjectured between the number of strata of a Datalog¬ program and the number of “coordination stages” require...
Previous studies of incomplete XML documents have identified three main sources of incompleteness – in structural information, data values, and labeling – and addressed data ...
We introduce a representation system for relational data based on algebraic factorisation using distributivity of product over union and commutativity of product and union. We giv...
We consider the problem of repairing unranked trees (e.g., XML documents) satisfying a given restriction specification R (e.g., a DTD) into unranked trees satisfying a given targ...