XML in a Nutshell, 3rd Edition

The XPath Data Model

XPath views each XML document as a tree of nodes. Each node has one of seven types:

Root

Each document has exactly one root node, which is the root of the tree. This node contains one comment node child for each comment outside the document element, one processing-instruction node child for each processing instruction outside the root element, and exactly one element node child for the root element. It does not contain any representation of the XML declaration, the document type declaration, or any whitespace that occurs before or after the root element. The root node has no parent node. The root node’s value is the value of the root element.

Element

An element node has a name, a namespace URI, a parent node, and a list of child nodes, which may include other element nodes, comment nodes, processing-instruction nodes, and text nodes. An element node also has a collection of attributes and a collection of in-scope namespaces, none of which are considered to be children of the element. The string-value of an element node is the complete, parsed text between the element’s start- and end-tags that remains after all tags, comments, and processing instructions are removed and all entity and character references are resolved.

Attribute

An attribute node has a name, a namespace URI, a value, and a parent element. However, although elements are parents of attributes, attributes are not children of their parent elements. The biological metaphor breaks down here. xmlns and ...