There are four data types in XPath 1.0:
Numbers
Strings
Booleans
Node-sets
These node types are supported in XPath 1.0:
The root node
Element nodes
Attribute nodes
Processing instruction nodes
Comment nodes
Text nodes
Namespace nodes
Here are some additional concepts from this chapter:
Document order is the order of nodes as they appear in the original document.
Documents are handled by XML processors as node trees.
Infosets hold the data that an XML document contains in standard form.
