CityGML is a profile of GML3, which implements an interoperable, multifunctional,
multi-scale and semantic 3D city model. This section presents
the highlights of CityGML, starting with general concepts in the first section.
CityGML covers the thematic objects which are relevant for city
models, including transportation objects like streets or traffic lights, or
vegetation objects. However, in this section the focus is on the most
important components of city models, on the building model and on the
Digital Terrain Model. Both are discussed in detail.
Initially, CityGML is specified using the graphical Unified Modeling
Language (UML) (see Booch et al. 1997). From UML diagrams, the XML
schemas are derived by applying the transformation rules given in Cox et
al. (2004). Thus, CityGML may be processed by standard GML3 readers.