[xsl] Categorise Node by Unique Attribute

[William Warby <untrusted@xxxxxxxxxxxx>]

Hi all.

I want to group nodes in an XML file, placing a heading above each 
category. The category is defined in an attribute which may be the same 
for a series of records. The code sample below shows what I want to do. 
I've been going round in circles trying combinations of variables, 
templates, for-each loops and I just can't seem to get a handle on the 
problem. Any help would be very gratefully received.

XML Source:

<authors>
  <author name="Steven King">
       <book genre="Drama" name="Book 1" />
       <book genre="Drama" name="Book 2" />
       <book genre="Drama" name="Book 3" />
       <book genre="Sci-Fi" name="Book 4" />
       <book genre="Sci-Fi" name="Book 5" />
   </author>
  <author name="Bill Bryson">
       <book genre="Travel" name="Book 1" />
       <book genre="Travel" name="Book 2" />
       <book genre="History" name="Book 3" />
   </author>
</authors>

Desired output:

<h2>Steven King</h2>
<h3>Drama</h3>
<ul>
   <li>Book 1</li>
   <li>Book 2</li>
   <li>Book 3</li>
</ul>
<h3>Sci-Fi</h3>
<ul>
   <li>Book 4</li>
   <li>Book 5</li>
</ul>
<h2>Bill Bryson</h2>
<h3>Travel</h3>
<ul>
   <li>Book 1</li>
   <li>Book 2</li>
</ul>
<h3>History</h3>
<ul>
   <li>Book 3</li>
</ul>


I am using classic ASP, MSXML2.DOMDocument.6.0