Hi, I'm pretty new to XSLT and I don't know how to approach this 
transformation problem I have.

I'm converting XML to XML from a very simple record-like format to an 
insanely complex highly nested format. I don't have any control over 
either format.

What I do have is a list of rules mapping input paths to output paths, e.g.

/rec/id1 => /aaa/bbb/ddd/fff
/rec/id2 => /aaa/bbb/ccc
/rec/id3 => /aaa/bbb/ddd/eee

I can code these rules individually easily enough but the problem is 
that when I apply to this input

<rec>
  <id1>hello</id1>
  <id2>and</id2>
  <id3>goodbye</id3>
</rec>

I get this output

<aaa><bbb><ddd><fff>hello</fff></ddd></bbb></aaa>
<aaa><bbb><ccc>and</ccc></bbb></aaa>
<aaa><bbb><ddd><eee>goodbye</eee></ddd></bbb></aaa>

when what I want is this

<aaa>
  <bbb>
   <ccc>and</ccc>
   <ddd>
    <eee>goodbye</eee>
    <fff>hello</fff>
   </ddd>
  </bbb>
</aaa>

Seems to me that I have to write some sort of generic merging and 
reordering code to post process the output, but I have no clue how to do 
that in XSLT.

Any clues on how to approach this problem will be greatly appreciated.

John