Research Of XML-Cycle Based On DTD

Acyclic database scheme designing is a new research field in relational database; it combines database theory with graph theory. Acyclic database has many good characteristic propertys, it becomes another important standard to evaluate the database pattern is superior or inferior. The cycle here means that some attributes are ambiguous in relational database, there are two or more paths when query about these attributes, so the cycle has formed. Cycle exist in the XML document in the same. If definition of some elements cannot display the meaning of element in XML document properly, there will be fuzzy result when query some element without context information, then we cannot declare the meaning of queried result, it is query ambiguity. This paper study normalization of XML document from a new point of view, define XML-cycle based on DTD, propose a determinant arithmetic if there is any cycle in DTD, propose a arithmetic of define new element to eliminate cyclic in DTD. Begin with studying the query ambiguity of XML document, the works of this paper is: First, analyze various DTD with cycle-structure in it, generalize the structure characteristic, and accordingly define XML-cycle based on DTD.According to the definition of XML-cycle, analyz DTD with XML-cycle further, discover the characteristic of DTD with XML-cycle that is some elements have more than one father element or the root element have father element. And propos a determinant arithmetic to check that if there is any XML-cycle in DTD. Second, put forward a method of eliminate the query ambiguity on the basis of analyzing. Propose an algorithm of define new element to eliminate cyclic in DTD on the basis of the characteristic of DTD with XML-cycle and the result of determinant arithmetic, make DTD satisfy X1NF. And point out the problems of DTD after XML-cycle is eliminated. Combining with the Algorithm of makeDTD satisfy X2NF and X3NF, propose an algorithm that make DTD satisfy XNF at last.The arithmetics proposed in this article can be embedded in some function module of XML editor or DTD editor; it is the meaning of practicality.