基于函数依赖的XML键的推理及其求解算法

The Reasoning and Algorithm about Keys for XML Based on Functional Dependency

键是数据库模式和概念设计的基础，是语义的一个重要组成部分。随着XML成为Web上一种通用的数据交换标准格式，将键的概念引入到XML领域就显得非常迫切。本文基于路径和树元组表达式，从数据库设计的角度出发，在XML函数依赖形式化定义的基础上给出XML键完整陆约束定义、XML绝对键和相对键的有效和完备的推理规则，并提出使用多项式时间求解XML候选键的算法，为XML数据库模式的规范化设计奠定了理论基础。

Key is the basis of database schema and concept designing. It is an important part of semantic world. As XML becomes a standard lorm for general data exchanging on Web, it is impending to introduce key to XML fields. In this paper, based on paths and tree tuples expressions and formalized definition lor XML functional dependency, from the point of database designing, the definition of XML key integrality constraints, the sound and complete inference rules to absolute key and relative key for XML, and the algorithm for XML candidate key in polynomial time are given. These establish theoretic foundation for normalized designing of XML database schema.