XPath SUMMARY!

XPath Introduction

XPath (XML Path Language) is a query language for selecting nodes from an XML document. It provides a way to navigate through elements and attributes in XML documents efficiently. XPath is widely used in technologies like XSLT, XQuery, and DOM parsing.

XPath Nodes

In XPath, the XML document is treated as a tree of nodes: - Element nodes (e.g., <book>) - Attribute nodes (e.g., category=”fiction”) - Text nodes (text content inside elements) - Namespace nodes - Processing instruction nodes - Comment nodes - Root node (entire document)

Example XML:

<library>
  <book category="fiction">
    <title>Harry Potter</title>
  </book>
</library>

XPath Syntax

XPath expressions are used to select nodes or node sets.

Common syntax: - / selects from the root node - // selects nodes anywhere in the document - @ selects attributes - [] applies conditions

Example XPath expressions:

/library/book/title          -> Selects the title of the book
//title                       -> Selects all title elements
/library/book[@category='fiction'] -> Selects books with category "fiction"
//@category                   -> Selects all category attributes

XPath Axes

Axes define the node relationships: - child:: selects all children - parent:: selects the parent - ancestor:: selects all ancestors - descendant:: selects all descendants - following-sibling:: selects siblings after the current node - preceding-sibling:: selects siblings before the current node - attribute:: selects attributes

Example:

child::book          -> Selects all child book elements
descendant::title    -> Selects all title descendants

XPath Operators

Operators in XPath allow complex queries: - | (Union) — combine results - +, -, *, div, mod — arithmetic - =, !=, <, >, <=, >= — comparison - and, or — logical operations

Example:

/library/book[price > 30]     -> Select books with price greater than 30
//title | //author            -> Select all title and author elements

XPath Examples

Here are some full XPath examples based on the XML below:

<library>
  <book category="fiction">
    <title>Harry Potter</title>
    <author>J.K. Rowling</author>
    <price>29.99</price>
  </book>
  <book category="science">
    <title>A Brief History of Time</title>
    <author>Stephen Hawking</author>
    <price>15.50</price>
  </book>
</library>

Examples:

/library/book/title
-> Selects all title elements of books.

/library/book[@category='science']/title
-> Selects the title of the science category book.

//price[text() > 20]
-> Selects price elements with values greater than 20.

/library/book[author='J.K. Rowling']/title
-> Selects the title of the book written by J.K. Rowling.