A document is a tree of nodes
Seven kinds of nodes:
The document itself. The root node’s children are the comments and processing instructions in the prolog and epilog and the root element of the document.
An element. Its children are all the child elements, text nodes, comments, and processing instructions the element contains. An element also has namespaces and attributes. However, these are not child nodes.
An attribute other than one that declares a namespace
The maximum uninterrupted run of text between tags, comments, and processing instructions. White space is included.
A processing instruction
A namespace mapping in scope on an element
The XPath data model does not include:
the document type declaration