Functional dependencies and inference rules for XML

The concept of functional dependency plays a fundamental role in relational databases where they are used in integrity enforcement and in database design. Similarly, these constraints will play fundamental role in XML as well. Recently XML functional dependencies (XFDs) have been intensively studied than other constraints for XML data. Since key is a special case of XFD, a formal definition of XFD that is able to specify keys and DTD (Data Type Definition) cardinality constraints is defined. A method for reasoning about these constraints and a set of inference rules for XFDs is proposed and proof correct.