基于Key的XML连续查询算法

普遍认为，XML将会取代Html成为数据表示和数据交换的主流标准，由于在线信息变化频繁，XML文档变化检测成为Internet查询系统、搜索引擎以及连续查询系统的关键技术．先前的研究多着眼于有序模式的XML文档，而无需模式的通用比较已经被证明是NP问题，目前针对无需模式的最好算法复杂度为多项式时间．本文提出了基于Key的变化检测算法，能够高效地检测无序模式XML文档的变化，算法复杂度为O(nlogn)，n为文档结点数．

Key-Based XML Algorithm for Continual Query

Over the next several years XML is likely to replace HTML as the standard web publishing language and data transportation format.Since online information changes frequently,being able to quickly detect changes in XML documents is important to Internet query systems,search engines,and continuous query systems.Most previous work in change detection on XML or other hierarchically structured data used the ordered tree,where change detection on unordered trees has been shown to be NP Complete in general case.It is well known that the best algorithm for unordered model achieves polynomial time in complexity.A key based algorithm is proposed,which can effectively detect changes in XML documents with an unordered model.The complexity of the algorithm is O(nlogn),where n is the total number of nodes in the document.The algorithm was analyzed,and some preliminary performance results were given.