reversing element ordering, with a caveat

[Howard Katz]

I have a series of books ordered chronologically by publication date, 1942
to 2009. I want to generate a file in which the books have the reverse
chronological ordering, 2009 to 1942, but with the caveat that books
*within* a particular year need to maintain the original document order
relative to that year. In the following, the catid attributes within a
particular year remain in ascending order after the transformation.  (The
catid's are used here only for demonstration purposes; they're not present
in the actual document.)

I'd be happy to see a solution either in XQuery or in XSLT. Here's some
sample input and the output.

Input:

<library>
	<book pubYear='1942' catid='1' >
		<otherStuff ... /></book>
	<book pubYear='1942' catid='2' >
		<otherStuff ... /></book>
	<book pubYear='1942' catid=' 3 ' >
		<otherStuff ... /></book>
	...

	<book pubYear='2009' catid=' 2011' >
		<otherStuff ... /></book>
	<book pubYear='2009' catid=' 2012 ' >
		<otherStuff ... /></book>
	<book pubYear='2009' catid=' 2013 ' >
		<otherStuff ... /></book>
</library>

Output:

<library>
	<book pubYear='2009' catid=' 2011' >
		<otherStuff ... /></book>
	<book pubYear='2009' catid=' 2012 ' >
		<otherStuff ... /></book>
	<book pubYear='2009' catid=' 2013 ' >
		<otherStuff ... /></book>
	...

	<book pubYear='1942' catid=' 1 ' >
		<otherStuff ... /></book>
	<book pubYear='1942' catid=' 2 ' >
		<otherStuff ... /></book>
	<book pubYear='1942' catid=' 3 ' >
		<otherStuff ... /></book>
</library>

TIA,
Howard