By considering design decisions hierarchically, exploration becomes a process of choosing which fork in the road to take as each decision is encountered. Typically, a sequential decision strategy is a heuristic approach—it is a rule of thumb that does not guarantee that the best alternative is found on the first pass. One cannot typically know that there is not a better design down some path that was not taken. As a result, most designers will explore several paths, may backtrack, and may explore several different sequences of decisions. Nevertheless, a collection of promising designs can usually be generated relatively efficiently by considering decisions hierarchically.

— Design: Creation of Artifacts in Society by Karl Ulrich