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A possible world of an incomplete database table is obtained by imputing values from the attributes (infinite) domain to the place of NULLs. A table satisfies a possible key or possible functional dependency constraint if there exists a possible ...${}_{\mathrm{}}$${}_{\mathrm{}}$${}_{\mathrm{}}$${}_{\mathrm{}}$${}_{\mathrm{}}$${}_{\mathrm{}}$$\mathrm{}\frac{}{}\mathrm{}$${}_{\mathrm{}}{}_{\mathrm{}}\frac{}{}$${}_{\mathrm{}}$

Incomplete and probabilistic database techniques are principled methods for coping with uncertainty in data. Unfortunately, the class of queries that can be answered efficiently over such databases is severely limited, even when advanced approximation ...

We study the complexity of various fundamental counting problems that arise in the context of incomplete databases, i.e., relational databases that can contain unknown values in the form of labeled nulls. Specifically, we assume that the domains of ...

Certain answers are a principled method for coping with uncertainty that arises in many practical data management tasks. Unfortunately, this method is expensive and may ex- clude useful (if uncertain) answers. Thus, users frequently resort to less ...

The inversion of data exchange mappings is one of the thorniest issues in data exchange. In this paper we study inverse data exchange from a novel perspective. Previous work has dealt with the static problem of finding a target-to-source mapping that ...

The notion of representation systems describes structures that are algebraically closed under queries. It has recently been realized that representation systems are highly relevant also in the context of data exchange. We extend the notion of ...

We show that relational algebra calculations for incomplete databases, probabilistic databases, bag semantics and why-provenance are particular cases of the same general algorithms involving semirings. This further suggests a comprehensive provenance ...

Snack-algebras - algebras introduced for modelling databases - are shown to be distributive replicas of dissemilattices.

(The paper was written while the author visited Iowa State University. Ames. Iowa in Fall 1995.)