Toyota’s SBCE process, however, differs significantly from either of the models in Figure 1. Design participants reason about, develop, and communicate sets of solutions in parallel and relatively independently. As the design progresses, they gradually narrow their respective sets of solutions based on additional information from development, testing, the customer, and other participants’ sets. As designs converge, participants commit to staying within the set(s), barring extreme circumstances, so that others can rely on their communication.