XQuery Terms
XQuery Terminology
Nodes
In XQuery, there are seven kinds of nodes: element, attribute, text, namespace, processing-instruction, comment, and document (root) nodes.XML documents are treated as trees of nodes. The root of the tree is called the document node (or root node).
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> <bookstore> (root 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> 
