Index: ogr/ogrsf_frmts/gml/drv_gml.html
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--- ogr/ogrsf_frmts/gml/drv_gml.html (revisione 23630)
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+## TopoSurface interpretation rules [polygons and internal holes]

+
+Starting since OGR 1.9.0 the GML driver is able to recognize two different interpretation
+rules for TopoSurface when some polygon does actually contains any internal hole:
+
+ - the previously supported interpretation rule assumed that:
+ - each TopoSurface may be represented as a collection of many Faces
+ *positive* Faces [i.e. declaring **orientation="+"**] are assumed to
+ represent the Exterior Ring of some Polygon.
+ *negative* Faces [i.e. declaring **orientation="-"**] are assumed to
+ represent an Interior Ring (aka *hole*) belonging to the latest declared
+ Exterior Ring.
+ - ordering any Edge used to represent each Ring is important: each Edge is expected
+ to be exactly adjacent to the next one.
+

+ - the new interpretation rule now assumes that:
+ - each TopoSurface may be represented as a collection of many Faces
+ - the declared
**orientation** for any Face has nothing to deal with Exterior/Interior Rings
+ - each Face is now intended to represent a complete Polygon, eventually including any possible Interior
+ Ring (
*holes*)
+ - the relative ordering of any Edge composing the same Face is completely not relevant
+

+

+
+The newest interpretation seems to fully match GML 3 standard recommendations; so this latest
+is now assumed to be the default interpretation supported by OGR.

+Using the **GML_FACE_HOLE_NEGATIVE** configuration option you can anyway select the
+actual interpretation to be applied when parsing GML 3 Topologies:
+
+ - setting
**GML_FACE_HOLE_NEGATIVE NO** (*default* option) will activate
+ the newest interpretation rule
+ - but explicitly setting
**GML_FACE_HOLE_NEGATIVE YES** still enables to activate
+ the old interpretation rule
+

+
## Encoding issues

Expat library supports reading the following built-in encodings :