Prototyping

1. Prototyping

2. Objectives • To survey the use of modeling in product design • To explain different kinds of prototypes • To list the uses of prototypes • To present prototyping risks and mitigation strategies

3. Topics • Modeling in product design • Prototypes • Horizontal and vertical • Throwaway and evolutionary • Low- and high-fidelity • Prototype uses • Prototyping risks

4. Modeling in Product Design Modeling is useful throughout product design. • Document problem domains • Explore stakeholder needs and desires • Test design constraints • Detect misunderstandings, and incomplete or inconsistent specifications • Generate design alternatives • Evaluate and select design alternatives • Record product designs

5. Prototypes A prototype is a special kind of model. • Represent a target (the product) • Must work in some way A prototype is a working model of part or all of a final product.

6. Horizontal & Vertical Prototypes • A horizontal prototype realizes part or all of a product’s user interface. • One program layer • Mock-ups • A vertical prototype does processing apart from that required to present a user interface. • Cuts across program layers • Proof of concept prototype

7. Throwaway and Evolutionary Prototypes • A throwaway prototype is developed as a design aid and then discarded. • Exploratory prototype • Quick to build • Risky to use in the final product • An evolutionary prototype is a prototype that becomes (part of) the final product. • Iterative development • More expensive to build • Difficult to build to handle change

8. Low- and High-Fidelity Prototypes • Fidelity is how closely a prototype represents the final product it models. • There is a continuum of fidelity • Low-fidelity prototypes • Paper or rough electronic prototypes • “Executed” by walking through interactions • Very quick and easy • High-fidelity prototypes • Usually electronic • Take longer to build (good tools help)

9. Prototype Uses 1 • Needs elicitation • Basis for discussion, jogs memory, inspires ideas • Usually throwaway horizontal paper prototypes • Needs analysis • Captures developers understanding of needs • Usually throwaway horizontal prototypes at various levels of fidelity • Requirements generation and refinement • Design alternatives • Explore new ideas • Often horizontal throwaway paper prototypes

10. Prototype Uses 2 • Requirements evaluation and selection • Usability studies • Requirements feasibility • Usually higher fidelity; sometimes vertical prototypes • Design finalization • Better for review than an SRS • Advisable to make high-fidelity evolutionary horizontal prototypes

11. Prototyping Risks • Using a throwaway prototype as the basis for development • Avoid making high-fidelity throwaway prototypes • Make it very clear to stakeholders that the prototype only appears to work • Fixation on appearance rather than function • Don’t use prototypes for functional needs elicitation • Use low-fidelity prototypes for needs elicitation • Prototype is “better” than the final product • Use low-fidelity prototypes • Ensure that high-fidelity prototypes are accurate representations

12. Summary • A variety of models are used for several tasks in product design. • A prototype is a working model of (part of) a final product. • Prototypes can be throwaway or evolutionary, horizontal or vertical, and have varying degrees of fidelity. • Prototypes are useful for needs elicitation, for alternative generation, evaluation, and selection, and for design finalization. • Risks attendant on the use of prototypes can usually be mitigated.