The complex and extensive nature of urban environments creates difficulties to the task of generating virtual models. However, the amount of information regarding urban areas available in digital format is an enabling condition to the automation of the modelling processes, thus reducing the amount of human intervention required.This paper presents a three-dimensional modelling system based on interoperable access to data in diverse formats and digital support. Data integration is achieved by the use of XML documents or invoking Web services in a distributed architecture.The system is driven by L-systems based modelling processes that automatically generate initial solutions for virtual environments. These initial solutions are, probably, characterised by a low level of realism, but can be incrementally improved.The modelling processes and data sources are specified in a declarative way, using documents based on an XML-schema called XL3D
