XSLT Filtering based on defined XML

Hi All,

Is there an elegant pattern via xslt to filter out an existing source
xml document based on the contents of another filter xml document?
For example:

Source xml doc:
<Root>
   <Node1>
      <Node11>
        <Node111/>
      </Node11>
      <Node12/>
   <Node2>
   ...

Filter xml doc:
<Root>
   <Node1>
     <Node111/>
   </Node1>
</Root>

Desired results:
<Root>
   <Node1>
     <Node111/>
   </Node1>
</Root>

Now the issue that I'm dealing with is that the filter xml doc is
dynamic.  That is, it can be different for any given xml source doc
configuration based on what another server source specifies.  I could
recursively build some dynamic xslt and add apply-templates for each
node and make use of copy and copy-of based on if a node has children
or not and then run that dynamically build transform on the xml doc
source...however, can anybody think of another way to do this?

Thanks in advance!