XML stands for eXtensible Markup Language. XML is a meta language based entirely on user-specified semantics. It is therefore possible to create a page structure with user-defined tags and a DTD or XML Schema to describe the data. In other words, the XML describes itself. XML was designed to store, carry, and exchange data; not to display data.
Example of XML document
catalog.xml
<catalog>
<cd>
<title>Atlantis</title>
<artist>DJ Aquarius</artist>
<country>USA</country>
<company>Independent</company>
<price>9.95</price>
<year>2001</year>
</cd>
<cd>
<title>Dance Anthems : Spring 2004 </title>
<artist>Ministry of Sound</artist>
<country>UK</country>
<company>Inspired</company>
<price>14.95</price>
<year>2004</year>
</cd>
<cd>
<title>A Lively Mind</title>
<artist>Paul Oakenfold</artist>
<country>USA</country>
<company>Maverick</company>
<price>13.99</price>
<year>2006</year>
</cd>
</catalog>
These tags are made up by the user to reflect the data, as opposed to HTML tags, which are structured to define language interpretation and do not change. Browsers come preconfigured with instructions specifying how to translate HTML tags. XML, on the other hand, is transformed into XHTML, or more XML, via an XSLT stylesheet. All the instructions for transformation are therefore contained in the XSLT stylesheet.
What is XSLT?
XSLT stands for eXtensible Stylesheet Language Translation. It’s a stylesheet used to translate XML in a similar way that CSS is used to define and extend HTML declarations.
Example of XSL stylesheet
catalog.xsl
<html>
<style type=”text/css”>
table, td { border: 1px solid #000; background-color: white }tr { background-color: silver }td { padding: 0.5em }
</style>
<body>
<h2>My CD Collection</h2>
<table>
<tr>
<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>
Styling XSLT with CSS
The following CSS was inserted to style the xslt stylesheet above:
<style type=\”text/css\”>
table, td { border: 1px solid #000; background-color: white }
tr { background-color: silver }
td { padding: 0.5em }
</style>
