Merging XML rowsets with matching attributes

I have an xml rowset defined similar to the following:

<root>
  <dataset1>
    <rows>
      <row id="0" title="Some Title" lookupValues="Something1;Something2"/>
      <row id="1" title="Some other title" lookupValues="Something1;Something3"/>
    </rows>
  </dataset1>
  <dataset2>
    <rows>
      <row lookupValue="Something1"/>
      <row lookupValue="Something2"/>
      <row lookupValue="Something3"/>
      <row lookupValue="Not Something"/>
    </rows>
  </dataset2>
</root>

and I'm trying to to a transform into a format more like the following:

<newroot>
  <rows>
    <row uniqueid="1" id="0" title="Some Title" lookupValue="Something1"/>
    <row uniqueid="2" id="0" title="Some Title" lookupValue="Something2"/>
    <row uniqueid="3" id="1" title="Some other title" lookupValue="Something1"/>
    <row uniqueid="4" id="1" title="Some other title" lookupValue="Something3"/>
  </rows>
</newroot>

Note the duplicate rows; this is a requirement for the app. Also note the dropping of the missed lookupValue row.

Does anyone know a truly efficient way of achieving this transform?

Thanks.