XPath Terminology
Nodes
In XPath, there are seven kinds of nodes: element, attribute, text, namespace, processing-instruction, comment, and document nodes.
XML documents are treated as trees of nodes. The topmost element of the tree is called the root element.
Look at the following XML document:
<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
<book>
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
</bookstore>
Example of nodes in the XML document above:
<bookstore> (root element node)
<author>J K. Rowling</author> (element node)
lang="en" (attribute node)
Atomic values
Atomic values are nodes with no children or parent.
Example of atomic values:
J K. Rowling
"en"
Items
Items are atomic values or nodes.
Relationship of Nodes
Parent
Each element and attribute has one parent.
In the following example; the book element is the parent of the title, author, year, and price:
<book>
<title>Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
Children
Element nodes may have zero, one or more children.
In the following example; the title, author, year, and price elements are all children of the book element:
<book>
<title>Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
Siblings
Nodes that have the same parent.
In the following example; the title, author, year, and price elements are all siblings:
<book>
<title>Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
Ancestors
A node's parent, parent's parent, etc.
In the following example; the ancestors of the title element are the book element and the bookstore element:
<bookstore>
<book>
<title>Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
</bookstore>
Descendants
A node's children, children's children, etc.
In the following example; descendants of the bookstore element are the book, title, author, year, and price elements:
<bookstore>
<book>
<title>Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
</bookstore>
