Multivalued Dependencies in XML

Functional dependencies (FDs) and multivalued dependencies (MVDs) play a fundamental role in relational databases where they provide semantics for the data and at the same time are the foundation for database design. Since XML documents are closely coupled with relational databases in that XML documents are typically exported and imported from relational databases, the study of FDs and MVDs in XML is of fundamental significance in XML research. In this paper we investigate the issue of defining multivalued dependencies in XML, a topic which to the best of our knowledge has not been previously investigated. We define multivalued dependencies in XML (XMVDs) and justify our definition by proving that, for a very general class of mappings from relations to XML, a relation satisfies an MVD if and only if the corresponding XML document satisfies the corresponding XMVD. Thus our definition of a XMVD in a XML document is a natural extension of the definition of a MVD in relations.