DOM is based on an implicit data model, which is similar to but not quite the same as the data models used by other XML technologies such as XPath, the XML Infoset, and SAX. Before we delve too deeply into the nitty-gritty details of the DOM API, it's helpful to have a higher level understanding of just what DOM thinks an XML document is.
According to DOM, an XML document is a tree made up of nodes of several types. The tree has a single root node, and all nodes in this tree except for the root have a single parent node. Furthermore, each node has a list of child nodes. In some cases, this list of children may be empty, in which case the node is called a leaf node.
There can also be nodes that are not part of the tree structure. For example, ...