In general, you should use the deferred implementation if your application needs to process large documents and if your application is not intending to traverse the whole tree.
一般而言，如果应用程序需要处理大型文档或者不大可能遍历整棵树时，应该使用这种延迟实现。
2
From this root node, you can traverse the entire XML tree.
从这个根节点，就可以遍历整个xml树。
3
Figure 10 illustrates how the location structure changes as we traverse the tree, here going down (always to the first left child), then right, then down.