A A partial or simulated approximation of the solution for the purpose of eliciting or verifying requirements with stakeholders. that is used to drill down into a proposed solution to uncover A usable representation of a need. and A usable representation of a solution. For more information see Key Terms (p. 14) and Requirements and Designs (p. 19). considerations through multiple layers of a solution that are not easily understood or that are not discernible on the surface. It may include interaction between several solution components.