Relaxed Functional Dependencies - A Survey of Approaches

Recently, there has been a renovated interest in functional dependencies due to the possibility of employing them in several advanced database operations, such as data cleaning, query relaxation, record matching, and so forth. In particular, the constraints defined for canonical functional dependencies have been relaxed to capture inconsistencies in real data, patterns of semantically related data, or semantic relationships in complex data types. In this paper, we have surveyed 35 of such functional dependencies, providing a classification criteria, motivating examples, and a systematic analysis of them

New Closure Operators and Lattice Representations for Multivalued Dependencies and Related Expressions

In Database Theory, Multivalued Dependencies are the main tool to define the Fourth Normal Form and, as such, their inference problem has been deeply studied; two related notions appearing in that study are a syntactical analog in propositional logic and a restriction that maintains to this logic the same relationship as Functional Dependencies do to Horn logic. We present semantic, lattice-theoretic characterizations of such multivalued dependencies that hold in a given relation, as well as similar results for the related notions just mentioned. Our characterizations explain better some previously known facts by providing a unifying framework that is also consistent with the studies of Functional Dependencies.Postprint (published version

Inconsistency and Incompleteness in Relational Databases and Logic Programs

The aim of this thesis is to study the role played by negation in databases and to develop data models that can handle inconsistent and incomplete information. We develop models that also allow incompleteness through disjunctive information under both the CWA and the OWA in relational databases. In the area of logic programming, extended logic programs allow explicit representation of negative information. As a result, a number of extended logic programs have an inconsistent semantics. We present a translation of extended logic programs to normal logic programs that is more tolerant to inconsistencies. Extended logic programs have also been used widely in order to compute the repairs of an inconsistent database. We present some preliminary ideas on how source information can be incorporated into the repair program in order to produce a subset of the set of all repairs based on a preference for certain sources over others

On Resolving Semantic Heterogeneities and Deriving Constraints in Schema Integration

Ph.DDOCTOR OF PHILOSOPH

Diversity, dependence and independence

We propose a very general, unifying framework for the concepts of dependence and independence. For this purpose, we introduce the notion of diversity rank. By means of this diversity rank we identify total determination with the inability to create more diversity, and independence with the presence of maximum diversity. We show that our theory of dependence and independence covers a variety of dependence concepts, for example the seemingly unrelated concepts of linear dependence in algebra and dependence of variables in logic.Peer reviewe