Research On Weak Functional Dependence For XML And Mondependent Set

With XML emerging, many new issues are proposed in database domain, and constraints of XML data is one of these issues. XML function dependency, logical implication are the foundation of the further research on XML normalization theory. The research of XML data schema began before long, though it had gained some research fruit, but yet didn't form uniform criterion and complete theory system. This paper analyzing and integrating the actuality in internal and external, researched the problems of XML function dependency and inference rules from a new point of view.Firstly, based on the definitions of DTD and XML tree given by M.Arenas et al., semantic of null value is introduced to XML, concepts of complete tree tuple, incomplete tree tuple, data value partial order and minimal extended tree are proposed. Based on it, the definition of weak functional dependency and implicationits are given.Secondly, Lien-Atzeni's axiom system of incomplete relations is extended to XML, a set of inference rules that based on XML tree tuples and fitting to XML weak functional dependence is given, rightness and completeness of the inference rules are also proved.Thirdly, the additivity of weak functional dependence is studied. The semantic of weak satisfaction is extended to functional dependence set, the definition of additivity of weak functional dependence is given, and the detemining algorithm of weak functional dependence additivity is proposed. Concept of XML mondependent set is given, and its connection with additivity is reseached.Finally, the property of mondependent set is reseached. Another defining method of mondependent set under canonical cover is given, based on it, adetermine algorithm of mondependent set is proposed, its corecteness and time complexity is analyzed. Characteristic of the closure of functional dependent set is discussed under mondependent set.