XML and XPath

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XML and XPath



What is XPath?
XPath is a major element in the XSLT standard.
XPath can be used to navigate through elements and attributes in an XML document.








XPath is a syntax for defining parts of an XML document
XPath uses path expressions to navigate in XML documents
XPath contains a library of standard functions
XPath is a major element in XSLT and in XQuery
XPath is a W3C recommendation




XPath Path Expressions
XPath uses path expressions to select nodes or node-sets in an XML document. These path
expressions look very much like the expressions you see when you work with a traditional computer file system.
XPath expressions can be used in JavaScript, Java, XML Schema, PHP, Python,
C and C++, and lots of other languages.

XPath is Used in XSLT
XPath is a major element in the XSLT standard.
With XPath knowledge you will be able to take great advantage of XSL.







XPath Example
We will use the following XML document:


<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
<book category="cooking">
 
<title lang="en">Everyday Italian</title>
 
<author>Giada De Laurentiis</author>
 
<year>2005</year>
 
<price>30.00</price>
</book>
<book category="children">
 
<title lang="en">Harry Potter</title>
 
<author>J K. Rowling</author>
 
<year>2005</year>
 
<price>29.99</price>
</book>
<book category="web">
 
<title lang="en">XQuery Kick Start</title>
 
<author>James McGovern</author>
 
<author>Per Bothner</author>
 
<author>Kurt Cagle</author>
 
<author>James Linn</author>
 
<author>Vaidyanathan Nagarajan</author>
 
<year>2003</year>
 
<price>49.99</price>
</book>
<book category="web">
 
<title lang="en">Learning XML</title>
 
<author>Erik T. Ray</author>
 
<year>2003</year>
 
<price>39.95</price>
</book>
</bookstore>
In the table below we have listed some XPath expressions and the result of the expressions:


XPath Expression
Result


/bookstore/book[1]
Selects the first book element that is the child of the bookstore element


/bookstore/book[last()]
Selects the last book element that is the child of the bookstore element


/bookstore/book[last()-1]
Selects the last but one book element that is the child of the bookstore element


/bookstore/book[position()<3]
Selects the first two book elements that are children of the bookstore element


//title[@lang]
Selects all the title elements that have an attribute named lang


//title[@lang='en']
Selects all the title elements that have a "lang" attribute with a value of "en"


/bookstore/book[price>35.00]
Selects all the book elements of the bookstore element that have a price element with a value greater than 35.00


/bookstore/book[price>35.00]/title
Selects all the title elements of the book elements of the bookstore element that have a price element with a value greater than 35.00



XPath Tutorial

You will learn a lot more about XPath in our XPath Tutorial.













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Reference: https://www.w3schools.com/xml/xml_xpath.asp