7.4.3. DescribeFeatureType¶
The DescribeFeatureType operation returns a schema
description of the feature types advertised by the 3D City
Database WFS instance. Which feature types are offered by the WFS is
controlled through the config.xml settings file (cf. Section 7.4.1.4).
The schema defines the structure and content of the features
(thematic and spatial attributes, nested features, etc.) as well as the
way how features are encoded in responses to GetFeature requests.
The following example shows a valid DescribeFeatureType operation requesting the XML Schema definition of the CityGML 1.0 Building feature type.
<?xml version="1.0" encoding="UTF-8"?>
<wfs:DescribeFeatureType service="WFS" version="2.0.0"
xmlns:wfs="http://www.opengis.net/wfs/2.0"
xmlns:bldg="http://www.opengis.net/citygml/building/1.0">
<wfs:TypeName>bldg:Building</wfs:TypeName>
</wfs:DescribeFeatureType>
The DescribeFeatureType operations takes the following XML attributes.
XML attribute
|
O / M
|
Default value
|
Description
|
service
|
M
|
WFS (fixed)
|
The service attribute indicates the
service type. The value “WFS” is fixed.
|
version
|
M
|
2.0.x
|
The version of the WFS Interface
Standard to be used in the
communication.
|
outputFormat
|
O
|
application/gml+xml;
version=3.1
|
Controls the format of the schema
description. By default, the request
results in a CityGML / GML 3.1.1
application schema. The outputFormat
attribute may also take the value
“application/json”, in which case the
response is a CityJSON schema document.
|
handle
|
O
|
The handle parameter allows a client to
associate a mnemonic name with the
request that will be used in exception
reports.
|
The <wfs:TypeName> child element of the DescribeFeatureType operation
identifies the feature type for which the XML Schema description is
requested. Be careful to use the correct spelling of the feature type
name (as specified by the CityGML standard) and to associate the name
with the correct CityGML XML namespace (see Section 7.4.1.4).
The <wfs:TypeName> element may
occur multiple times to request schema definitions of several feature
types in a single DescribeFeatureType operation. If the <wfs:TypeName>
element is omitted, then the complete base schema is returned by the WFS.
The DescribeFeatureType operation can alternatively be invoked through HTTP GET with key-value pairs.
http[s]://[host][:port]/[context_path]/wfs?
SERVICE=WFS&
VERSION=2.0.2&
REQUEST=DescribeFeatureType&
TYPENAME=bldg:Building,tran:Road
The following KVP parameters are supported.
KVP parameter
|
O / M
|
Default value
|
Description
|
SERVICE
|
M
|
WFS (fixed)
|
see above
|
VERSION
|
M
|
2.0.x
|
see above
|
NAMESPACES
|
O
|
Used to specify namespaces and their
prefixes. The format shall be
xmlns(prefix,escaped_url).
|
|
TYPENAME
|
M
|
A comma-separated list of feature types
to describe.
|
|
OUTPUTFORMAT
|
O
|
application/gml+xml;
version=3.1
|
see above
|
The TYPENAME attribute lists the feature types to describe. Similar to an
XML-encoded request, both the feature type names and the XML namespaces
must be correct. XML namespaces and their prefixes can be specified
using the NAMESPACES attribute. If you use default CityGML prefixes
though, the NAMESPACES attribute can be skipped (see Section 7.4.1.4).