Transcript Chapter 2: Objects and Primitive Data

Prototyping
© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley
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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
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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
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Modeling in Product Design
Modeling is useful throughout product
design.
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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
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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.
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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
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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
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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)
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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
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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
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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
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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.
© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley
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