Local XML functional dependencies

Keys and functional dependencies play a fundamental role in relational databases where they are used in integrity enforcement and in database design. Similarly, these constraints will play a fundamental role in XML and recently keys and functional dependencies in XML have been denned. In this paper we extend the previous definition of functional dependencies in XML to local functional dependencies in XML. Local functional dependencies (LFDs) are functional dependencies which hold only in a certain part of an XML document and not in the whole document. We also define, and prove correct, axioms for reasoning about the implication of LFDs in XML. Finally, we examine the relationship between LFDs and keys and show that the recently introduced concept of a relative key is a special case of a LFD