http://www.someserver.com/wfs.cgi&
SERVICE=WFS&
VERSION=1.1.0&
REQUEST=GetFeature&
PROPERTYNAME=InWaterA_1M/wkbGeom,InWaterA_1M/tileId&
TYPENAME=InWaterA_1M&
FILTER=<Filter xmlns:gml="http://www.opengis.net/gml"><Within><PropertyName>InWaterA_1M/wkbGeom</PropertyName><gml:Envelope><gml:lowerCorner>10,10</gml:lowerCorner><gml:upperCorner>20 20</gml:upperCorner></gml:Envelope></Within></Filter>