sample mapnik xml

processed_p.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE Map[]>
<Map 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">

<Style name="water" filter-mode="first">
  <Rule>
    <PolygonSymbolizer fill="green" />
  </Rule>
</Style>

<Layer name="water"
  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>water</StyleName>
    <Datasource>
       <Parameter name="table">processed_p</Parameter>
       <Parameter name="dbname">processed_p</Parameter>
       <Parameter name="type">postgis</Parameter>
       <Parameter name="extent">-20037508 -20037658,20037508 18464390.6665912</Parameter>
    </Datasource>
</Layer>

</Map>