01.11.2011 
A data model describes the structure, th conditions and behaviour of data including 
the semantics. 
To describe a data model, it needs a modelling language which can be grafical (e.g. 
UML) or 
textual (e.g. GML, INTERLIS). 
There exist different levels of data models:
- conceptual 
model: describes the data in its structure and conditions in a system independent 
manner, based on a concept and its semantic of the real world.
 
- implementation model: describing 
the structure in a system dependent language that 
describes the data how it is implemented in a specific system.