EN/CityGML-Tutorial/chapter-1:-Intro-CityGML.md

+In order to describe a city model, CityGML utilizes thematic modules. The base module is the CityGML Core which gets extended by defined thematic modules such as Building, Bridge, Vegetation, Transportation, WaterBody, Relief, LandUse, Appearance etc. The building model defines the geometric and semantic properties of a building in CityGML. A building or a building part can be modeled as Solid (B-rep) or MultiSurface. The semantic objects for a BoundarySurface geometry in LOD2 are: RoofSurface, WallSurface, GroundSurface, and ClosureSurface.
+
+![CityGML-2](uploads/1d896b57e0343a215e1b404463334145/CityGML-2.png)
+
+CityGML also defines attributes for every city object. The standard defines two types of attributes: Schema attributes and generic attributes. Schema attributes are part of the schema definition of each thematic module. The building schema defines the attributes: function, yearOfConstruction, yearOfDemolition, measuredHeight, storeysAboveGround etc. Generic attributes are defined by the user to store additional information in a city object. There is no restriction in the number or the names of the generic attributes as long as they conform to the XML syntactic rules.
+
+* [Chapter 1.1: CityGML Appearance Module](./chapter 1:Intro CityGML/Appearance)