mapnik/tests/data/good_maps/xinclude/layers.xml

<?xml version="1.0" encoding="utf-8"?>
<Include  xmlns:xi="http://www.w3.org/2001/XInclude">

    <Layer name="world_borders" srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over">
        <StyleName>world_borders_style</StyleName>
        <StyleName>point_style</StyleName>
        <Datasource>
            <Parameter name="file">../../shp/world_merc.shp</Parameter>
            <Parameter name="type">shape</Parameter>
        </Datasource>
    </Layer>

</Include>