A premise can take three forms:

• fuzzy,    
• valued,  
• crisp.     

A crisp premise characterizes qualitative geographical data. For instance:

• ``the soil is clayey'', or
• ``the soil is not clayey'', and
•  more generally:

A valued premise characterizes quantitative geographical data. For instance:

• ``the altitude is 1527 meters'',
• ``the distance is in the range 1000 to 2000 meters'', and
•  more generally:

A fuzzy premise characterizes both qualitative and quantitative geographical data. For instance:

• ``the soil is fertile'',
• ``the altitude is high'', and
•  more generally:

The attribute allows spatial characteristics to be introduced. They are obtained from the shape of the geographical objects such as:

• surface,
• perimeter,
• orientation,
• compactness...