The knowledge base is built by means of an interface , a rule compiler written in PROLOG programming language. The expert expresses his knowledge in natural language but with predefined keywords related to

• objects that can be extracted from GIS:
• valley, slope, ridge, plateau,... related to DEM,
• road, village,... related to topographic map,
• clay, rocky,... related to soils map.
  
  
• knowledge description capabilities. For example, keywords for:
• relational characteristics :
• Far away,
• Near,
• Around,
• Upper ,
• Bottom,
• West, ...
  
• uncertainty expression :
• Only (+1),
• Principally (+0.8)
• Frequently (+0.5),
• Uncommon (-0.6), ...

Then the interface constructs the corresponding production rules.

Remember that we have two types of rules :

• "pointwise" rules based on the pixel context itself
• "structural" rules based on the shape, surface, spatial context of the pixel, etc.