Creating XML/KML documents from single tables

Hi
I would be most grateful if someone could help me create an xml doc in the form:

<root>
  <layer name = 'x1'>
    <marker id="35"
class="1"><Point><coordinates>-3.04,53.56,0</coordinates></Point></marker>
    <marker id="35"
class="4"><Point><coordinates>-2.04,55.56,0</coordinates></Point></marker>
  </layer>
  <layer name = 'x2'>
    <marker id="35"
class="3"><Point><coordinates>-3.44,57.56,0</coordinates></Point></marker>
  </layer>
</root>

This will be created from a single table of point geometries where
each belongs to a layer, e.g. x1 or x2 etc. The layer a geometry
belongs to is stored in a varchar column called layername.

Creating the marker tags is easily done using the query:
# select xmlelement(name marker, xmlattributes(gid as id, typeid as
class), askml(the_geom)) from poi

Or creating a list of layers is also simple:
#select xmlelement(name layer, xmlattributes(layername as name)) from
poi group by layername

However I cannot work out how to insert more than one child node into
a layer element.

Thanks

Will T