Normalization for DTD

A well designed DTD is very important for XML applications, which should avoid the occurrence of redundant information in documents In this paper XML is extended with functional dependencies, which are fundamental to semantic specification The functional dependency here can be both absolute and relative, and the key is just a special case of it The definition of logical implication is studied and a sound and complete set of inference rules are presented Based on functional dependency, the concept of normalized DTD is defined and an algorithm for converting DTD into a corresponding normalized one is provided