Abstract: XML due to has merits of powerful representation ability,self-description and agility,etc.,and object-oriented methods also have strong modeling ability,the introduction of the object-oriented notion into XML database can enhance query language modeling ability that based on XML schema.So result size estimation of value predication in object-oriented XML query is a multiple attributes dependent problem.It is difficult to use one method to estimate result size,for multiple attributes in XML involve not only the value data,but also the structural information.To solve the problem,this paper proposes estimation result size method that based on histogram and integrate the query tree stucture in process of estimation.

摘要：

由于XML具有丰富的表达能力、自描述性和灵活性等优点,而面向对象的概念又具有很强的建模能力,将面向对象的概念引入到XML可以提高XML模式语言的建模能力。而面向对象XML数据查询的值匹配条件的查询代价估计问题是一种典型的多元素查询条件的代价估计问题。XML数据的值分布与其他值信息的分布有关,还与XML数据的结构信息有关,很难使用某种单一的代价估计方法。针对以上问题,提出了一种基于直方图,在估计过程中结合查询树结构的代价估计方法。