XML in a Nutshell, 3rd Edition

Generic Versus Specific DOM Interfaces

To simplify different types of document processing and enable efficient implementation of DOM by some programming languages, there are actually two distinct methods for accessing a document tree from within the DOM Core: through the generic Node interface and through specific interfaces for each node type. Although there are several distinct types of markup that may appear within an XML document (elements, attributes, processing instructions, and so on), the relationships between these different document features can be expressed as a typical hierarchical tree structure. Elements are linked to both their predecessors and successors, as well as their parent and child nodes. Although there are many different types of nodes, the basic parent, child, and sibling relationships are common to everything in an XML document.

The generic Node interface captures the minimal set of attributes and methods that are required to express this tree structure. A given Node contains all of the tree pointers required to locate its parent node, child nodes, and siblings. The next section describes the Node interface in detail.

In addition to the generic Node interface, the DOM also defines a set of XML-specific interfaces that represent distinct document features, such as elements, attributes, processing instructions, and so on. All of the specific interfaces are derived from the generic Node interface, which means that a particular application can switch methods ...