XSLT  (EXtensible Sytlesheet Language Transformations) is a tool that can be used to transform XML documents into other formats most commonly of which is XHTML. XSLT is a stylesheet that defines how to display or output the data from the XML. Using XSLT you can sort, filter, and manipulate the data as needed iterating of data elements and their child elements. Below is a short example of how to sort an XML data file based on 2 elements.

To start things off we need an xml data file. In our example we are going to use books. You will notice that in addition to the xml data we specify the xml-stylesheet to utilize which we will create next.

     
	Patrick Rothfuss
			
	DAW
	2007
   
     
	Trudi Canavan
			
	EOS
	2004
   
     
	Trudi Canavan
			
	Orbit
	2009
   
     
	Jim Butcher
			
	ACE
	2090
   
     
	Jim Butcher
			
	ROC
	2010
   
     
	Brandon Sanderson
			
	TOR
	2009
   

Next we will create an XSL Stylesheet that will be used to transform the XML Data into a XHTML page that displays the information in a table sorted by author followed by the title.

    
    
    

  

   

       
Title
       
Author
       
Publisher
       
Year
   
  
 
  

   
	  
       

       

       

       

    
   
  

In the above example we define the style sheet to iterate over each book element in the xml using the xsl:for-each tag. Then we immediately tell it to sort on the author field and secondly by the title field by use of the xsl:sort tag.

The end result is an html table as shown below:

You can sort on as many elements as you want simply adding addtional xsl:sort tags. Full information on the available properties like order can be found at w3schools