Validating XML Documents
In the preceding section, you saw how to traverse the tree structure of a DOM document. However, if you simply follow that approach, you'll find that you will have quite a bit of tedious programming and error checking. Not only do you have to deal with whitespace between elements, but you also need to check whether the document contains the nodes that you expect. For example, suppose you are reading an element:
<font> <name>Helvetica</name> <size>36</size> </font>
You get the first child. Oops...it is a text node containing whitespace "\n ". You skip text nodes and find the first element node. Then you need to check that its tag name is "name". You need to check that it has one child node of type Text. You move on to ...