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XPath Nodes

Nodes​

Nodes​

There are seven kinds of nodes in XPath:

  • Root: it is the topmost element of the document with child elements below it.
  • Element (<tagname> ... </tagname>): these type follows the root node and can contain attribute in it.
  • Attribute (<tagname attribute="value">): this can be assigned below the element or root node.
  • Text: it represents the text written inside an element node.
  • Namespace: it matches namespace for all the nodes. This is defined at the beginning of the document in which the root element is declared.
  • Processing-instruction (<? ?>): this specifies the instruction for the application and can be used anywhere in the XML document.
  • Comment (<comment> </comment>): this node specifies the comment part for the particular code that is not processed by any programming language compiler.

An XML document can be specified as a tree of nodes. The highest element in the tree is called the root element.

Representation of nodes as a tree structure

Consider this example:

<?xml version="1.0"  encoding="UTF-8"?>  
<?xml-stylesheet type="text/css" href="style.css"?>

<bookstore>
	<book>
		<title lang="en">A Great Book</title>
		<author>Tutorial Reference</author>
		<year>2022</year>
	</book>
</bookstore>
<comment>This is a comment</comment>

We have that:

  • <bookstore> is the root element node.
  • <author>Tutorial Reference</author> is an element node.
  • Tutorial Reference is a text node.
  • lang="en" is an attribute node.
  • <?xml-stylesheet type="text/css" href="style.css"?> is a processing-instruction node.
  • <comment>This is a comment</comment> is a comment node.

Atomic values​

Atomic values are nodes with no children or parent.

For example:

Tutorial Reference  
  
"en"

Relationship of Nodes​

Parent​

Each element and attribute has one parent which is a top element of the respective element or attribute.

For example, the <book> element is the parent of <title>, <author> and <year> elements

<?xml version="1.0"  encoding="UTF-8"?>  

<bookstore>
	<book>
		<title lang="en">A Great Book</title>
		<author>Tutorial Reference</author>
		<year>2022</year>
	</book>
</bookstore>

Children​

Element nodes can have zero, one or more children.

For example, <title>, <author> and <year> elements are children of the <book> element

<?xml version="1.0"  encoding="UTF-8"?>  

<bookstore>
	<book>
		<title lang="en">A Great Book</title>
		<author>Tutorial Reference</author>
		<year>2022</year>
	</book>
</bookstore>

Siblings​

Nodes that have the same parent are known as siblings.

For example, <title>, <author> and <year> elements are siblings because they have the same parent element <book>

<?xml version="1.0"  encoding="UTF-8"?>  

<bookstore>
	<book>
		<title lang="en">A Great Book</title>
		<author>Tutorial Reference</author>
		<year>2022</year>
	</book>
</bookstore>

Ancestors​

The parent of a node or the parent of the parent, etc. is specified as the ancestor.

For example, the <book> element is the parent of <title>, <author> and <year> elements

<?xml version="1.0"  encoding="UTF-8"?>  

<bookstore>
	<book>
		<title lang="en">A Great Book</title>
		<author>Tutorial Reference</author>
		<year>2022</year>
	</book>
</bookstore>

Descendants​

The children of a node or the children of children, etc. are specified as the descendants.

For example, <book>, <title>, <author> and <year> elements are descendents of the <bookstore> element

<?xml version="1.0"  encoding="UTF-8"?>  

<bookstore>
	<book>
		<title lang="en">A Great Book</title>
		<author>Tutorial Reference</author>
		<year>2022</year>
	</book>
</bookstore>

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