1© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

PrototypingPrototyping

2© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

ObjectivesObjectives

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

TopicsTopics

Modeling in product design Prototypes

• Horizontal and vertical• Throwaway and evolutionary• Low- and high-fidelity

Prototype uses Prototyping risks

4© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

Modeling in Product Modeling in Product DesignDesign

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

PrototypesPrototypes

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

Horizontal & Vertical Horizontal & Vertical PrototypesPrototypes

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

Throwaway and Throwaway and Evolutionary PrototypesEvolutionary 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© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

Low- and High-Fidelity Low- and High-Fidelity PrototypesPrototypes

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

Prototype Uses 1Prototype 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© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

Prototype Uses 2Prototype 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© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

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

SummarySummary 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.