The process of redistricting involves the division of a land surface into two or more pieces. In a political setting, the districts thus formed provide groups of voters that elect the same public officials. Other types of redistricting applications include the formation of school districts, transportation districts, or water management districts.
In this work we describe a knowledge-based expert system, Grouper, as a solution to the redistricting problem. A number of key issues are addressed by the solution, including equality of population, contiguity, and graphical display of possible districts. In addition, we outline a method (the Grouper approach) for dramatically reducing the complexity of the redistricting problem by limiting activity to a specific level of detail.
A PC-based, prototype solution, implemented using the M.1 expert system shell, is described with emphasis on techniques for minimizing search. An annotated Grouper session is included. Lastly, there is a discussion of the far-reaching significance of the redistricting problem and promising uses or extensions of the Grouper system in this regard.