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sub-menus are also fully configurable. This way it is possible to construct application specific operator 
sets. • 
Figure 2. The VGIS design 
• Powerful, complex operations 
The operations offered to the user are no isomorphic mapping of the operations of the underlying GIS. 
Rather they are custom-made to each application. These operations are independent of whatever data 
structure is used. Necessary transformations are initiated by VGIS and performed by the underlying GIS.