© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3 Topics  Modeling in product design  Prototypes Horizontal and vertical Throwaway and evolutionary Low- and high-fidelity  Prototype uses  Prototyping risks

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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.

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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)

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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.