The <appearance>
parameter filters appearances by their theme. To keep an appearance in the target dataset, the value of its app:theme attribute simply has to be enumerated using a <theme>
subelement. The string values must match exactly.
The app:theme attribute in CityGML is optional and thus can be null. To be able to also express whether appearances having a null theme should be exported, the <appearance>
parameter offers another subelement <nullTheme>
, which is of type Boolean. If set to true, appearances with a null theme are exported, otherwise not (default).
The following query exports road features and appearances with theme summer and winter. Since <nullTheme>
is set to false, appearances lacking an app:theme attribute are not exported.
<query>
<typeNames>
<typeName>tran:Road</typeName>
</typeNames>
<appearance>
<nullTheme>false</nullTheme>
<theme>summer</theme>
<theme>winter</theme>
</appearance>
</query>