Data mapping / loading (?)

[Jeff Rafter <jeffrafter@earthlink.net>]

Sorry for the vague subject-- I have been searching for a simple way to load
data from one XML file into another and haven't found exactly what I am
looking for.  What I want to do is load an XML file with data values
(source) and load an XML file with some content (dest) and then move
contents from source to dest.  I would like to create a third "mapping" file
that specifies how to move the data from one to the other, most likely using
XPath.  The following is a simplified example of what I am looking for

source.xml
=======
<source>
  <value1>10</value1>
</source>

dest.xml
======
<dest>
  <question>Five plus five equals?</question>
  <answer name="value1"></answer>
</dest>

mapping.xml
=========
<mapping>
  <source href="source.xml"/>
  <dest href="dest.xml"/>
  <assign source="source/value1" dest="dest/answer[@name='value1']">
</mapping>

I know it is most likely possible using XSLT but I haven't figured out how
to do it without copying the whole destination document-- which seems like
overkill when I only want to change a few nodes.  Is XSLT the answer? Anyone
have any ideas?

Thanks in advance,
Jeff Rafter