using <make-absolute-uris> on the output of a <directory-list>

I just started using Xproc, and I am very excited by the features it  
has to offer.  I recently ran into what I *think* is a simple  
problem.  Here's the setup:

…

I have the combined the outputs of several <directory-list> steps into  
one document that looks something like the following:

<directory name="nameOfDir" xml:base="file:/path/to/nameOfDir">
	<directory name="anotherDir" xml:base="file:/path/to/nameOfDir/ 
anotherDir">
		<file name="name-of-file.ext" />
	</directory>
	
	<file name="another-file.ext" />
</directory>

Note the following:

all <directory> elements have an @xml:base present, with a properly  
url-encoded path.
unlike the above example…
the output is in the namespace xmlns:c="http://www.w3.org/ns/xproc- 
step".  I didn't feel like typing the prefix for the short example  
above.  :)
many of my files and directories have spaces and other non-url- 
friendly characters in their @names.  (This does not apply to the  
value of @xml:base on the <directory>s.)
when I attempt to run <make-absolute-uris match="file/@name" />  
afterwards, I get a long mess of java IllegalArgumentExceptions.  I'm  
guessing it has to do with the characters that are illegal for URIs,  
but I'm still new to XProc so I'm not sure how to solve it.

I'm using:

Calabash
v0.9.14
Oxygen XML Editor
v10.3
(includes Saxon 9, if it matters)
Mac OS X
v10.5 (“Leopard”)

…

I'd be very grateful if someone could point me in the right direction!

I have a feeling the solution to this is probably really simple…but  
I've already toyed around with various options for a few hours with no  
luck.  :(



—Tony