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Supported GML Versions

GML 3.1.1

  • GML 3.1.1 application schemas are supported for WFS 1.1.0.
  • Clients must specify WFS 1.1.0 in requests because the GeoServer default is WFS 2.0.0.
  • GET URLs must contain version=1.1.0 to set the WFS version to 1.1.0.

GML 3.2.1

  • GML 3.2.1 application schemas are supported for WFS 1.1.0 and (incomplete) WFS 2.0.0.
  • Some WFS 2.0.0 features not in WFS 1.1.0 such as GetFeatureById are not yet supported.
  • Clients using WFS 1.1.0 must specify WFS 1.1.0 in requests and select the gml32 output format for GML 3.2.1.
  • To use WFS 1.1.0 for GML 3.2.1, GET URLs must contain version=1.1.0 to set the WFS version to 1.1.0 and outputFormat=gml32 to set the output format to GML 3.2.1.
  • The default WFS version is 2.0.0, for which the default output format is GML 3.2.1.
  • All GML 3.2.1 responses are contained in a WFS 2.0.0 FeatureCollection element, even for WFS 1.1.0 requests, because a WFS 1.1.0 FeatureCollection cannot contain GML 3.2.1 features.

Secondary namespace for GML 3.2.1 required

GML 3.2.1 WFS responses are delivered in a WFS 2.0.0 FeatureCollection. Unlike WFS 1.1.0, WFS 2.0.0 does not depend explicitly on any GML version. As a consequence, the GML namespace is secondary and must be defined explicitly as a secondary namespace. See app-schema.secondary-namespaces for details.

For example, to use the prefix gml for GML 3.2, create workspaces/gml/namespace.xml containing:

<namespace>
    <id>gml_namespace</id>
    <prefix>gml</prefix>
    <uri>http://www.opengis.net/gml/3.2</uri>
</namespace>

and workspaces/gml/workspace.xml containing:

<workspace>
    <id>gml_workspace</id>
    <name>gml</name>
</workspace>

Failure to define the gml namespace prefix with a secondary namespace will result in errors like:

java.io.IOException: The prefix "null" for element "null:name" is not bound.

while encoding a response (in this case one containing gml:name), even if the namespace prefix is defined in the mapping file.

GML 3.2.1 geometries require gml:id

GML 3.2.1 requires that all geometries have a gml:id. While GeoServer will happily encode WFS responses without gml:id on geometries, these will be schema-invalid. Encoding a gml:id on a geometry can be achieved by setting an idExpression in the mapping for the geometry property. For example, gsml:shape is a geometry property and its gml:id might be generated with:

<AttributeMapping>
    <targetAttribute>gsml:shape</targetAttribute>
    <idExpression>
        <OCQL>strConcat('shape.', getId())</OCQL>
    </idExpression>
    <sourceExpression>
        <OCQL>SHAPE</OCQL>
    </sourceExpression>
</AttributeMapping>

In this example, getId() returns the gml:id of the containing feature, so each geometry will have a unique gml:id formed by appending the gml:id of the containing feature to the string "shape.".

If a multigeometry (such as a MultiPoint or MultiSurface) is assigned a gml:id of (for example) parentid, to permit GML 3.2.1 schema-validity, each geometry that the multigeometry contains will be automatically assigned a gml:id of the form parentid.1, parentid.2, ... in order.

GML 3.3

The proposed GML 3.3 is itself a GML 3.2.1 application schema; preliminary testing with drafts of GML 3.3 indicates that it works with app-schema as expected.