In order to better incorporate prototyping efforts into software-development practice, several fundamental issues have to be addressed in order to identify the right prototypology, for example:

• Appropriate fidelity. Discuss different fidelities of prototyping and their con-tribution to the software-development process with regards to the externaliza-tion of functional and non-functional requirements.
• Pressure of time and budget. Determine prototypes that can be developed within time and budget constraints in order to overcome objections to early-stage prototyping.
• UI development fragmentation. Identify the kind of prototypology (Schrage 1999) that can take client and supplier relationships into account and become part of contract-forming.
• UI specification support. Consider forms of prototyping that can become rec-ognized as well-engineered models that evolve into specifications and final products.
• Adequate traceability. Externalize the interdependency of models and design, turning the UI development into a transparent engineering process.