The original (shaded) problem is considered for a solution along three
competing scenarios: The "red" scenario calls for extending the
original problem. The extended problem is divided into two parts. One
part is attacked through abstraction, the other is solved directly.
The "green"
solution calls for an abstract definition of the original problem, then
extending the abstract problem, and solving the extended problem by
division. The "blue" solution strategy calls for division of the
original problem. One part is solved directly, the other is solved by
division.
