Functional dependencies for XML

Abstract

In this paper we address the problem of how to extend the definition of functional dependencies (FDs) in incomplete relations to XML documents. An incomplete relation is said to strongly satisfy a FD if every completion of the relation, obtained by replacing all null values by data values, satisfies the FD in the ordinary sense. We propose a syntactic definition of strong FD satisfaction in a XML document (called a XFD) and then justify it by proving that for a very general class of mappings of a relation into a XML document, a relation strongly satisfies a unary FD if and only if the XML document also strongly satisfies the equivalent XFD. © Springer-Verlag Berlin Heidelberg 2003.