MapServer LAYER>CLASSITEM>CLASS>EXPRESSION Object

If you wish to use more complicated styles for say OS MasterMap layers then you can use the following which will colour according to the value of a field name using EXPRESSION. It is also advisable to have a CLASS entry at the bottom of the list as a “catch all” style for the layer:

POLYGON – OS MasterMap GoLoader

CLASSITEM "OSMMSTYLE_NAME"
CLASS
     EXPRESSION "buildingFill"
     STYLE
         COLOR 255 204 153
         OUTLINECOLOR 204 204 204
     END
END
CLASS
     EXPRESSION "multipleSurfaceFill"
     STYLE
         COLOR 255 255 204
         OUTLINECOLOR 204 204 204
     END
END
CLASS
     EXPRESSION "0001 Building outline"
     STYLE
         COLOR 0 0 0
         WIDTH 2
   	 END
END

POLYGON – OS MasterMap TranspOSe / SuperpOSe

CLASSITEM "Legend"
CLASS
     EXPRESSION "0321 Building"
     STYLE
         COLOR 255 204 153
         OUTLINECOLOR 204 204 204
     END
END
CLASS
     EXPRESSION "0385 Nonconiferous - scattered"
     STYLE
         COLOR 0 0 0
         OUTLINECOLOR 204 204 204
         SYMBOL "0385Scattered" #[Draws a bitmap fill type]
     END
END

POLYLINE – OS MasterMap GoLoader

CLASSITEM "OSMMSTYLE_NAME"
CLASS
     EXPRESSION "defaultTopographicLine"
     STYLE
         COLOR 102 102 102
     END
END
CLASS
     EXPRESSION "buildingLine"
     STYLE
         COLOR 0 0 0
         WIDTH 2
     END
END

POLYLINE – OS MasterMap TranspOSe / SuperpOSe

CLASSITEM "Legend"
CLASS
      EXPRESSION "0030 Obstructing feature"
      STYLE
         COLOR 102 102 102
      END
END
CLASS

      EXPRESSION "0001 Building outline"
      STYLE
         COLOR 0 0 0
         WIDTH 2
      END
END