Note
These preference settings only apply to CityGML exports.
Both the 3D City Database and the Importer/Exporter are capable of handling XLinks. If the CityGML input document that is imported into the 3D City Database contains XLink references to features and/or geometries, then this information is kept in the database in order to be able to reconstruct the XLinks when the data is exported again. This is also the default behavior.
Export preferences – XLinks.
Depending on the target application that consumes the exported CityGML dataset, this default behavior may be disadvantageous though, especially if the target application cannot follow and resolve XLink references. In such cases, the XLinks preference settings let a user change the default behavior so that the referenced objects are exported by value rather than by reference. Put differently, instead of an XLink reference, a copy of the original feature or geometry is placed into the CityGML dataset. This necessarily requires that the gml:id of the copy is different from the gml:id of the original object because identical gml:id values are not allowed in the same dataset. The Importer/Exporter takes care of this issue and creates new gml:id values for the copies based on UUID values.
The user can define the behavior for exporting XLinks differently for
features [1] and geometries [2]. The settings allow providing a
prefix string that will be used when creating new gml:id values
(default: "ID_") and whether the original gml:id should be
appended to the newly created one. Only for features, the user can
additionally choose to store the original gml:id as <ExternalReference>
property in the copied feature.