Prototyping is a requirement technique frequently used for communication between customers and developers. Software prototypes help to understand users' expectations, but they are often seen as disposable artifacts because it is not easy to manage the transfer of knowledge from prototypes to software models or code. This chapter studies whether suitable solutions already exist for exploiting the knowledge acquired during the building of prototypes in the early phases of the lifecycle. The objective is addressed by means of a systematic literature review of approaches offering solutions for transforming software prototypes into analysis models. We propose a characterization schema for comparing them and describing the current state-of-the-art. The results reveal a need for more automated solutions that are more economical in terms of time and effort for transforming prototypes into models and thereby ensuring traceability between requirements and design artifacts.