More sophisticated methods of preliminary nature for both raster and vector categorical maps
have been proposed in the research literature, such as Schylberg (1993), Su et al. (1997) and Jaakkola (1998) for raster
data, or Muller and Wang (1992), de Berg et al. (1998) for vector models respectively. However, they need further improvement
and integration into a coherent framework and workflow if the generalization of categorical maps is to be
solved more comprehensively