7.3.4. Constraints settings¶

The <constraints> element of the config.xml allows for defining constraints on dedicated WFS operations.

<constraints>
  <countDefault>10</countDefault>
  <currentVersionOnly>true</currentVersionOnly>
  <exportCityDBMetadata>false</exportCityDBMetadata>
  <stripGeometry>false</stripGeometry>
  <lodFilter mode="and" searchMode="depth" searchDepth="2">
    <lod>2</lod>
    <lod>3</lod>
  </lodFilter>
</constraints>

countDefault

The <countDefault> constraint restricts the number of city objects to be returned by the WFS to the user-defined value, even if the request is satisfied by more city objects in the 3D City Database. The default behavior is to return all city objects matching a request. If a maximum count limit is defined, then this limit is automatically advertised in the server’s capabilities document using the CountDefault constraint.

currentVersionOnly

City objects can be marked as being terminated in the 3DCityDB using the attribute terminationDate without having to physically delete them from the database. This allows keeping the object history in the database and querying previous object versions based on timestamps. The current version of a city object can be simply identified by the fact that the column TERMINATION_DATE of the CITYOBJECT is not set. By default, the WFS only returns the current version of a city object in responses to GetFeature requests by automatically adding a filter expression on the terminationDate attribute. If you want to change this default behaviour, set the <currentVersionOnly> flag to false (default: true).

exportCityDBMetadata

The <exportCityDBMetadata> (default: false) flag allows exporting the metadata properties LINEAGE, UPDATING_PERSON, LAST_MODIFICATION_DATE and REASON_FOR_UPDATE of city objects stored in the table CITYOBJECT. Since these properties are not defined by CityGML, the WFS uses a CityGML Application Domain Extension (ADE) to include the properties in the response document.

stripGeometry

When setting <stripGeometry> to true (default: false), the WFS will remove all spatial properties from a city object before returning the city object to the client. Thus, the client will not receive any geometry values.

lodFilter

The <lodFilter> constraint defines a server-side filter on the LoD representations of the city objects. When using this constraint, city objects in a response document will only contain those LoD levels that are enumerated using one or more <lod> child elements of <lodFilter>. Further LoD representations of a city object, if any, are automatically removed. If a city object satisfies a query but does not have a geometry representation in at least one of the specified LoD levels, it will be skipped from the response document and thus not returned to the client.

The default behavior of the LoD filter can be adapted using attributes on the <lodFilter> element. The mode attribute defines how the selected LoDs should be evaluated and can take one of the values shown described below.

Table 7.3 Available filter modes¶
Filter mode	Description
or	City objects having a spatial representation in at least one of the selected LoDs will be exported. Additional LoD representations of the city object that do not match the user selection are not exported.
and	Only city objects having a spatial representation in all of the selected LoDs will be exported. Additional LoD representations of the city object that do not match the user selection are not exported.
minimum	This is a special version of the Or mode that only exports the lowest LoD representation from the matching ones. The exported LoD may therefore differ for each city object.
maximum	This is a special version of the Or mode that only exports the highest LoD representation from the matching ones. The exported LoD may therefore differ for each city object.

The default mode value is or. When setting the searchMode attribute to depth, then you can use the additional searchDepth attribute to specify how many levels of nested city objects shall be considered when searching for matching LoD representations. If searchMode is set to all, then all nested city objects will be considered (default: searchMode = depth, searchDepth = 1).

Note

The more levels you enter for the searchDepth attribute, the more complex the resulting SQL queries for the 3DCityDB will get.