Research On XML Functional Dependency And Inference Rules Under Incomplete Information

XML (eXtensible Markup Language) has become one of the primary standards for data exchange and representation on the Internet. Now XML document is as database to store data. Presently many studies on XML document are only according to node with definite value, but not according to node with indefinite value. In the paper, incomplete information is introduced into XML document, which make XML document with much function to express semantic of real world.There are too many unknown factors in the real world. Similar to relational database and XML document under incomplete information, in order to reduce the data redundancy and abnormity for inserting, deleting and updating data. Functional dependency of XML under incomplete information is important. Therefore it has important theoretic significance and practical value to the research on XML functional dependency and XML functional dependency inference rules under incomplete information.This paper studies the functional dependency of XML under incomplete information with DTDs as their schemas and investigates by expression a tree tuple representation. The research on XML functional dependency and XML functional dependency constraints under incomplete information are given. The main contributions of paper are as follow:In the paper, tree nodes are divided into three kinds: element node, attribute node and text node. Incomplete information is introduced to attribute node and text node. The relations between nodes are also studied as well as the relation between tree tuples. XML functional dependencies under incomplete information are presented based on these.XML Functional dependencies under incomplete information are presented based on path expression and tree tuple and make further research on XML functional dependency inference rules under incomplete information. And give a sound and complete set of inference rules of XML functional dependency. And hold conditions of functional dependency under incomplete information are studied the possibility of becoming functional dependency under complete information.XML partial functional dependency and complete functional dependency are presented based on holding conditions of functional dependency. The definitions of strong holding conditions of complete functional dependency and weak holding conditions of complete functional dependency are defined and are also studied the possibility of becoming complete functional dependency under complete information. Algorithms of these are given.The concepts of the key for XML under incomplete information are given. An algorithm of solving candidate key for XML under incomplete information is presented and validity, terminability and time complexity of that are proved.