The Internet Encyclopedia (Volume 3)

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142 PROTOTYPING

Customer

Input / Feedback

Analysis &

(Re-)design

Test / Release Build / Extend

Project Start

Product Release

Evolutionary Spiral Model

Figure 1: The spiral development model.

updates to the system’s specifications, evaluation of ex-

isting modules for reuse, careful engineering and testing,

and subsequent customer evaluation. Even if initial pro-

totypes are not extended or reused, analysis and design

can produce specifications that are useful for a full-scale

implementation. Iterative prototyping fits a general form

of the Spiral Model, a development process model first

proposed by Boehm (1988); see Figure 1.

Flexible Product Development and the

Evolutionary Development Model

Web-based applications are just one example of systems

that are developed rapidly and evolve constantly over

time. Many other types of applications are created in

dynamic, unstable environments where technology and

customer requirements are in constant flux. High-quality

software can be developed in such an environment with

the use of iterative, evolutionary prototyping in a flexible

development process.

Early Prototyping in Product Development

A study of 29 completed development projects (MacCor-

mack, Verganti, & Iansiti, 2001) showed that the creation

of an early, incomplete prototype for customer evaluation

is an important predictor of software quality in dynamic,

unstable environments. After release of the first proto-

type, the development team must work to integrate the

customer’s feedback into the software design as it evolves

towards the final deliverable. This implies an evolutionary

development model, where active development of the final

product begins before the final requirements are known.

A series of evolutionary prototypes may be constructed

and evaluated before the requirements are frozen for

a major release of the product. Evolutionary develop-

ment will be more successful when the team has made

a substantial investment in a flexible, modular architec-

ture that supports rapid adjustments to an evolving prod-

uct design. Team members with past experience on sev-

eral different projects and software versions are more

likely to thrive in an evolutionary development environ-

ment.

A Flexible Development Process

The total time from project start to market introduction

(lead time) can be divided intoconcept timeandresponse

time(Iansiti & MacCormack, 1997). Concept time is the

window of opportunity for introducing requirements into

the system concept, and matching the technology with

users and application context. Response time is the time

taken to produce the deliverable system after the sys-

tem concept is frozen. In a traditional software devel-

opment process, system implementation does not begin

until all the requirements have been frozen. In a more

flexible model, implementation (e.g., evolutionary proto-

typing) begins before the requirements are frozen, and

response time can be shortened significantly. When sev-

eral incremental product versions are to be developed, it is

important to minimize the response time (during which

requirements are frozen). In the most dynamic formu-

lation, a flexible development process will constantly ac-

quire new information about customer requirements, test

alternative design solutions, and integrate both into co-

herent, high quality products. In a study by MacCormack

(2001), the software system with the earliest beta release

and the greatest number of beta releases—Netscape Nav-

igator 3.0—also received the highest score for perceived

software quality. See Figure 2.

Infrastructure Requirements

The flexible development process requires an investment

in development infrastructure, primarily in version con-

trol and testing. Organizations that have demonstrated

success with rapid product cycles, such as Netscape and

Requirements

Analysis & Design

Implementation

Requirements

Analysis & Design

Implementation

Traditional Approach

Flexible Approach

Project

Start

Market

Introduction

Concept Time Response

Time

Concept Time Response Time

Iteration

Figure 2: A flexible approach to development.