The geometry type of a feature class can be specified in a .gfs
file used by OGR to map from a GML document to a simple feature schema. The following numbers can be used to specify a specific geometry type:
-2147483647 Point25D
-2147483646 LineString25D
-2147483645 Polygon25D
-2147483644 MultiPoint25D
-2147483643 MultiLineString25D
-2147483642 MultiPolygon25D
0 Geometry
1 Point
2 Line
3 Polygon
4 MultiPoint
5 MultiLineString
6 MultiPolygon
100 No Geometry
<GMLFeatureClass>
<Name>Address</Name>
<ElementPath>Address</ElementPath>
<GeometryType>1</GeometryType>
<SRSName>EPSG:27700</SRSName>
...
</GMLFeatureClass>
For a complete list see the OGR source.