The DOM treats the XML document as tree-structure. Each attribute,element and text in the XML document represents a node in the tree.

The terms "parent" and "child" are used to describe the relationships between node. Some nodes may have child node, while other nodes do not have children (leaf nodes).

Because the XML data is structured in a tree form, it can be traversed without knowing the exact structure of tree and without knowing the type of data contained within

Notice that the root element in XML document above is named <bookstore>. All other elements in the document are contained within <bookstore> tag.

The <bookstore> element represent the root node of the DOM tree.

The root node <bookstore> holds four <book> child node.

The first <book> child node also holds four children: <title>, <author>, <year>, and <price>, which contain one text node each, "Everyday Italian", "Giada De Laurentiis", "2005", and "30.00".

IMPORTANT! Text is always stored in text node. A common error in DOM processing is to navigate to an element node and expect it to contain text. However, even the simplest element node has text node under it. For example, in <year>2005</year>, there is an element node (year), and a text node under it, which contain the text (2005).

The following image illustrate a fragment of the DOM node tree from the XML document above: