Geonovum shows how to model an Application Domain Extension of CityGML in UML

Contributed by: 
Linda van den Brink, Geonovum

Geonovum, Netherlands has the task to provide better access to geo-information in the public sector. To fulfil this task, we at Geonovum develop and manage the required geo-standards. Of course we base our geo-standards on the international ISO and OGC geo-standards. 

Recently, we developed IMGeo (Information Model Geography): a national standard for 2D and 3D topography containing object definitions for large scale representations of roads, water, land use/land cover, bridges, tunnels etc. Because IMGeo was found to be very similar to the OGC City Geography Markup Language (CityGML) Encoding Standard, we decided to define it as a CityGML extension.

Like all our information models, we modeled IMGeo in UML (Unified Modeling Language). The CityGML standard describes how to model an additions to the standard as an "Application Domain Extension" (ADE). But this description focuses on how to extend the CityGML GML application schemas, not on modeling an ADE in UML.

Therefore we set off for some pioneering work. Along the way we got valuable input from several CityGML and UML modeling experts. Based on those discussions and our own requirements and insights, we came up with a CityGML IMGeo ADE modeled in UML, from which GML application schemas can be derived automatically. We recorded our experiences and lessons learned, which are now published in the form of an OGC Discussion Paper, Modeling an application domain extension of CityGML in UML, with the intention of making this a Best Practice. We are very excited about sharing our work with the standards community!


Visualisation of CityGML-IMGeo encoded data: CityGML Level of Detail (LOD) 2