7.3.3. Operations settings¶

The operations settings are used to define the operation-specific behavior of the WFS.

<operations>
  <requestEncoding>
    <method>KVP+XML</method>
    <useXMLValidation>true</useXMLValidation>
  </requestEncoding>
  <GetFeature>
    <outputFormats>
      <outputFormat name="application/gml+xml; version=3.1"/>
      <outputFormat name="application/json"/>
    </outputFormats>
  </GetFeature>
</operations>

Request encoding

The <requestEncoding> element determines whether the WFS shall support XML-encoded and/or KVP-encoded requests. The desired method is chosen using the <method> child element that accepts the values KVP, XML and KVP+XML (default: KVP+XML). When setting the <useXMLValidation> child element to true, all XML encoded operation requests sent to the WFS are first validated against the WFS and CityGML XML schemas. Requests that violate the schemas are not processed but instead a corresponding error message is sent back to the client. Although XML validation might take some milliseconds, it is highly recommended to always set this option to true to avoid unexpected failures due to XML issues.

GetFeature operation

With this version of the WFS interface, the only operation that can be further configured is the <GetFeature> operation. You can choose the available output formats that can be used in encoding the response to the client. The value “application/gml+xml; version=3.1” is the default and basically means that the response to a GetFeature operation will be purely XML-encoded (using CityGML as encoding format with the version specified in the feature type settings, cf. Section 7.3.2). In addition, the WFS can advertise the output format “application/json”. In this case, the response is delivered in CityJSON format. CityJSON is a JSON-based encoding of a subset of the CityGML data model.

Note

The WFS can only advertise the different output formats in the capabilities document. It is up to the client though to choose one of these output formats when requesting feature data from the WFS.

For CityGML, the following additional options are available.

Table 7.1 Output format options for CityGML.¶
Option	Description
`prettyPrint`	Formats the XML response document using additional line breaks and indentations (boolean true / false, default: false).

The CityJSON output format options are presented below.

Table 7.2 Output format options for CityJSON.¶
Option	Description
`prettyPrint`	Formats the JSON response document using additional line breaks and indentations (boolean true / false, default: false).
`significantDigits`	Maximum number of digits for vertices (integer, default: 3). Identical vertices are snapped.
`transformVertices`	Apply the CityJSON-specific compression (boolean true / false, default: false).
`generateCityGMLMetadata`	Adds an attribute called CityGMLMetadata that contains CityGML-specific metadata like the data types of generic attributes (boolean true / false, default: true).
`removeDuplicateChildGeometries`	CityJSON does not support reusing or referencing geometries. If geometries are reused within a city object in the database (e.g. between a Building and its BuildingInstallation child), they will be duplicate in the CityJSON output. Use this option to remove duplicate geometries from child objects. If the child object does not have any remaining geometry after removing the duplicates, it will be removed as well (boolean true / false, default: false).

The options are simply added beneath the corresponding <outputFormat> element and are applied to all response documents of the WFS in that format. The following snippet illustrates the use of the CityJSON format options.

<outputFormat name="application/json">
  <options>
    <option name="prettyPrint">true</option>
    <option name="significantDigits">5</option>
    <option name="transformVertices">true</option>
    <option name="generateCityGMLMetadata">true</option>
    <option name="removeDuplicateChildGeometries">true</option>
  </options>
</outputFormat>