SPECIAL TOPICXML

Introducing XML XML (eXtensible Markup Language)

◦ A language used to create structured documents

XML vs HTML◦ XML is designed to transport and store data (carry)◦ HTML was designed to display data (show)◦ Shares common structure with HTML documents

◦ Elements are indicated with markup tags that contain textual content; element names are descriptive

◦ A markup tag can contain attributes that describe a feature of the element, and a single root element contains all other elements in the document

Introducing XML XML does not DO anything. XML was created to structure, store, and transport information.

The following example is a note to Tove, from Jani, stored as XML<note>

< to>Tove</to>< from>Jani</from>< heading>Reminder</heading>< body>Don't forget me this weekend!</body>

< /note>

XML Tree Structure With XML You Invent Your Own Tags

◦ the XML language has no predefined tags

XML documents form a tree structure that starts at "the root" and branches to "the leaves".

<root><child>

<subchild>...

Introducing XML

XML declarationIt defines the XML version (1.0) and the encoding used (UTF-8).

Single root element (students)

Student, name, and photo elements and the id and grade attributes provide information about individual students

Syntax Ruleso Must have closing tags

o Case sensitive tags

o Proper tag nesting

o Must have a Root element

o Attributes must be quoted

o Uses HTML comments

o Special symbols > < & ‘ “o Use entity references: &lt; &gt;

Syntax Rules Comments are similar to HTML comment

<!-- comment -->

White-space is Preserved in XML

Naming rules◦ XML elements must follow these naming rules:◦ Names can contain letters, numbers, and other characters◦ Names cannot start with a number or punctuation character◦ Names cannot start with the letters xml (or XML, or Xml, etc)◦ Names cannot contain spaces◦ Any name can be used, no words are reserved

XML Elements An XML element is everything from (including) the element's start tag to (including) the element's end tag

An element can contain:◦ other elements◦ text◦ attributes◦ or a mix of all of the above

<bookstore>< book category="CHILDREN">

<title>Harry Potter</title><author>J K. Rowling</author><year>2005</year><price>29.99</price>

< /book>< /bookstore>

XML attributes XML elements can have attributes.

◦ Attributes provide additional information about an element.<file type="gif">computer.gif</file>

XML Elements vs. Attributes

Take a look at these examples:

< person sex="female"><firstname>Anna</firstname><lastname>Smith</lastname>

< /person>

< person><sex>female</sex><firstname>Anna</firstname><lastname>Smith</lastname>

< /person>

Attributes vs. Elements Some of the problems with using attributes are:

◦ attributes cannot contain multiple values (elements can)◦ attributes cannot contain tree structures (elements can)◦ attributes are not easily expandable (for future changes)

Attributes are difficult to read and maintain ◦ Use elements for data, and attributes for information that is not

relevant to the data

Namespaces XML Namespaces provide a method to avoid element name conflicts

Defined by the xmlns attribute

Tags that are not HTML tags have the prefix xsl, identified by the namespace xmlns:xsl="http://www.w3.org/1999/XSL/Transform":

Name conflicts in XML can easily be avoided using a name prefixxmlns:h="http://www.w3schools.com/html4">

xmlns:f="http://www.w3schools.com/furniture"><h:table><f:table>

eXtensible Style sheet Language Translation.XSLT

Styles Can use a CSS style sheet to format an XML document

<?xml-stylesheet type="text/css" href=“style.css"?>

Better approach is to use XSL (eXtensible Stylesheet Language)◦ can transform an XML document into HTML, using◦ XSLT (eXtensible Stylesheet Language Transformation)

<?xml-stylesheet type="text/xsl" href=“style.xsl"?>

Transforming XML with XSLT

Extensible Stylesheet Language Transformation (XSLT)◦ A style language developed for XML documents◦ Allows developers to easily transform contents of an XML

document into another document format◦ A more efficient approach to transforming an XML

document into HTML format than working with the document object model

The <xsl:template> Element

The match attribute is used to associate a template with an XML element

<xsl:template match="/">

match="/" indicates the stylesheet template applies to the entire XML file

<?xml version="1.0" encoding="ISO-8859-1"?>< xsl:stylesheet version="1.0“ xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

< xsl:template match="/"> <html> <body> <h2>My CD Collection</h2> <table border="1"> <tr bgcolor="#9acd32"> <th>Title</th> <th>Artist</th> </tr> <tr> <td>.</td> <td>.</td> </tr> </table> </body> </html> < /xsl:template>< /xsl:stylesheet>

<xsl:value-of> Used to extract the value of an XML element and add to output.

<?xml version="1.0" encoding="ISO-8859-1"?>< xsl:stylesheet version="1.0“ xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

< xsl:template match="/"> <html> <body> <h2>My CD Collection</h2> <table border="1"> <tr bgcolor="#9acd32"> <th>Title</th> <th>Artist</th> </tr> <tr> <td> <xsl:value-of select="catalog/cd/title"/></td> <td> <xsl:value-of select="catalog/cd/artist"/></td> </tr></table></body></html>< /xsl:template>

< /xsl:stylesheet>

The <xsl:for-each> Element

Allows you to do looping

<?xml version="1.0" encoding="ISO-8859-1"?>< xsl:stylesheet version="1.0“ xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> < xsl:template match="/"> <html> <body> <h2>My CD Collection</h2> <table border="1"> <tr bgcolor="#9acd32"> <th>Title</th> <th>Artist</th> </tr> <xsl:for-each select="catalog/cd"> <tr> <td> <xsl:value-of select="title"/> </td> <td> <xsl:value-of select="artist"/> </td> </tr> </xsl:for-each> </table> </body> </html>< /xsl:template>< /xsl:stylesheet>

XSLT <xsl:sort> Element

used to sort the output

<?xml version="1.0" encoding="ISO-8859-1"?>< xsl:stylesheet version="1.0"xmlns:xsl="http://www.w3.org/1999/XSL/Transform">< xsl:template match="/"><html><body><h2>My CD Collection</h2><table border="1"><tr bgcolor="#9acd32"><th>Title</th><th>Artist</th></tr><xsl:for-each select="catalog/cd"><xsl:sort select="artist"/><tr><td> <xsl:value-of select="title"/> </td><td> <xsl:value-of select="artist"/> </td></tr></xsl:for-each></table></body></html>< /xsl:template>< /xsl:stylesheet>

XSLT <xsl:if> Element

used to put a conditional test against the content of the XML file

<?xml version="1.0" encoding="ISO-8859-1"?>< xsl:stylesheet version="1.0"xmlns:xsl="http://www.w3.org/1999/XSL/Transform">< xsl:template match="/"><html><body><h2>My CD Collection</h2><table border="1"><tr bgcolor="#9acd32"><th>Title</th><th>Artist</th></tr><xsl:for-each select="catalog/cd"> <xsl:if test="price &gt; 10"> <tr> <td><xsl:value-of select="title"/></td> <td><xsl:value-of select="artist"/></td> </tr> </xsl:if></xsl:for-each></table></body></html>< /xsl:template>< /xsl:stylesheet>