MAP                                                                                                                                                     
  STYLE                                                                                                                                                 
    # define a named style with global visibility                                                                                                       
    NAME "some_style"                                                                                                                                   
    ...                                                                                                                                                 
  END                                                                                                                                                   
  ...                                                                                                                                                   
  LAYER                                                                                                                                                 
    NAME "uses_a_style"                                                                                                                                 
    CLASS                                                                                                                                               
       # a name instead of a block means 'use the named style directly'                                                                                 
       STYLE "some_style"                                                                                                                               
       ...                                                                                                                                              
    END                                                                                                                                                 
  END                                                                                                                                                   
  LAYER                                                                                                                                                 
    NAME "extends_a_style"                                                                                                                              
    CLASS                                                                                                                                               
      STYLE                                                                                                                                             
        # inside a style block, pull in properties from another style                                                                                   
        # then make custom changes for this LAYER/CLASS                                                                                                 
        EXTENDS "some_style"                                                                                                                            
        ...                                                                                                                                             
      END                                                                                                                                               
    END                                                                                                                                                 
  END                                                                                                                                                   
END