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

@@ -14,7 +14,8 @@ CityGML Model Stuttgart-Stöckach, the model itself was created by L. Rothengass
 
 ## CityGML Core
 
-The following UML diagram defines the CityGML Core (CityGML 2.0).  
+The following UML diagram defines the CityGML top level class hierarchy (CityGML 2.0 standard document, fig. 23, p51). 
+ 
 ![image](uploads/c0637b17c8b839570b05ca5f4f235a1c/image.png)
 
 A _City Model_ is a collection of _cityObjectMembers_. Each CityGML Module defines specific _CityObjects_ such as _Building_ objects, _Vegetation_ objects etc. Every _CityObject_ has a fixed set of specific attributes as specified in the UML model, and an _Appearance_ do define its visual properties. _GenericAttributes_ can be used to define additional attributes that are not explicitly specified in the UML model itself.