On mercredi 23 janvier 2019 11:42:19 CET Alessandro Pasotti wrote: > Thanks for all the comments! > > I understand that it depends on the schema, what confuses me is the > assertion by Andrea in the (quite old) cited email that "GML and WFS > explicitly avoid the use of "xs:nil", I could not find any authoritative > support for that claim. > > So, if that is not the case, we should probably fix QGIS Server's > DescribeFeatureType to return something like this (for a nillable element): > > <element type="long" name="id_long" minOccours="0" /> > > And for the getFeature response, in case the value is NULL: > > <qgs:id xsi:nil="true" />
If you want to be able to set xsi:nil="true", the XSD element declaration must have the nillable="true" attribute. minOccurs="0" is to allow the element to be completely absent. > > How does it sounds? > > > On Wed, Jan 23, 2019 at 11:02 AM Even Rouault <[email protected]> > > wrote: > > Recent versions of OGR make a difference between : > > > > - a missing XML element, that will be represented in OGR as a "unset > > field") > > (allowed if the schema has minOccurs="0") > > - and a XML element set to <foo xsi:nil="true"/>, that will be represented > > in > > OGR as a NULL field value (allowed if the schema has nillable="true") > > > > ( see https://trac.osgeo.org/gdal/wiki/rfc67_nullfieldvalues ) > > > > The same for JSon actually, between a property that doesn't appear at all, > > or > > which is set to null. > > > > Example, given foo.json with > > > > { "type": "FeatureCollection", > > > > "features": [ > > > > { "type": "Feature", "properties": { "a": 1, "null_prop": null }, > > > > "geometry": null }, > > > > { "type": "Feature", "properties": { "b": 2 }, "geometry": null } > > > > ] > > > > } > > > > $ ogr2ogr foo.gml foo.json -f gml > > > > $ cat foo.gml > > <?xml version="1.0" encoding="utf-8" ?> > > <ogr:FeatureCollection > > > > xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; > > xsi:schemaLocation="http://ogr.maptools.org/ foo.xsd" > > xmlns:ogr="http://ogr.maptools.org/"; > > xmlns:gml="http://www.opengis.net/gml";> > > > > <gml:boundedBy><gml:null>missing</gml:null></gml:boundedBy> > > > > <gml:featureMember> > > > > <ogr:foo fid="foo.0"> > > > > <ogr:a>1</ogr:a> > > <ogr:null_prop xsi:nil="true"/> > > > > </ogr:foo> > > > > </gml:featureMember> > > <gml:featureMember> > > > > <ogr:foo fid="foo.1"> > > > > <ogr:b>2</ogr:b> > > > > </ogr:foo> > > > > </gml:featureMember> > > > > </ogr:FeatureCollection> > > > > $ ogr2ogr out.json foo.gml > > > > $ ogrinfo foo.gml -al > > INFO: Open of `foo.gml' > > > > using driver `GML' successful. > > > > Layer name: foo > > Geometry: Unknown (any) > > Feature Count: 2 > > Layer SRS WKT: > > (unknown) > > Geometry Column = geometryProperty > > fid: String (0.0) NOT NULL > > a: Integer (16.0) > > null_prop: String (0.0) > > b: Integer (16.0) > > OGRFeature(foo):0 > > > > fid (String) = foo.0 > > a (Integer) = 1 > > null_prop (String) = (null) > > > > OGRFeature(foo):1 > > > > fid (String) = foo.1 > > b (Integer) = 2 > > > > And yes this is not WFS or GML specific, but XML + XML-Schema generic. > > > > -- > > Spatialys - Geospatial professional services > > http://www.spatialys.com -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ QGIS-Developer mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
