摘要： 在XML的树模型基础上，提出查询是一个有序的带标记树、数据库是一个有序的带标记树集合的思想，对于查询的回答是一个或几个从查询树结点到数据库结点的同态映射；对一般意义下的XML树模型进行了形式化改造，并且基于改造后的XML树模型构造了查询；最后，阐述了这一工作的意义。

关键词: 数据库, 树模型, 可扩展标记语言, 查询

Abstract: The paper proposes some notions on XML documents and XML query. Then it formalizes the notions. These notions are ordered trees with labels for XML documents, a set of the trees for XML database and that answers for an XML query are homomorphism from query tree nodes to database nodes. In the end of the paper the significance of the work is explained.

中图分类号: 

• TP311.13