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The Prototyping Approach
Techniques for prototype application
Types of Information Systems Sprague & Watson, DSS for Management, Prentice Hall, 1996
Type I (Procedure)• High volume• Low transaction cost• Well structured• Measurable• Process & efficiency• Data• Clerical
Type II (Goal)• Low volume• High trans. value• Poorly structured• Hard to measure• Goal & effectiveness• Concepts• Mgrs, professionals
IS Development Approaches
• Systems Development Life Cycle• Information Center (DSS)• Object and Component
Type ILarge Systems
• Intercommunications among applications
• Formal methodologies• CASE technologies• Purchased products• Outsourcing
Type ISDLC
• Type I systems• Large and Costly• Cost justified• Formal stages of evaluation• Stages carefully reviewed and
formally approved• Data, Process, Communications
Type IIInformation Center (DSS)
• Type II systems• Relatively small and inexpensive• Value justified• Prototyping and evolutionary design• Data, Dialog, Model
Prototyping
“It is easier to tell what you don’t like about an existing system than to
describe what you would like in an imaginary one”
A.M. Jenkins, 1983
Choice
Life Cycle Prespecification
possible Changes expensive Good project
communication Static model OK Rigorous approach
useful Iteration
unacceptable
Prototype Prespecification
difficult Quick tools work Communications gap Animated model
needed Rigor after
requirements Iteration accepted
The Prototyping Process
IdentifyInitial
Requirements
DevelopSystem
Use andEvaluate
Document and Install
Iterate
Prototyping Life Cycle
Determine suitability for prototypingIdentify basic needsDevelop working modelDemonstrate and solicit refinementsRevise and redemonstrateClean up and document
Assumptions
All requirements cannot be specifiedQuick build tools are availableCommunications gap between
builders and usersActive models are requiredRigorous approaches are appropriate
once requirements are knownIteration is valuable
Use Prototyping If
Life cycle too slowScope of project manageable
30 screensSmall team: 1-2 users/designers50 attributes
User not sure of specificationsUser satisfaction very importantReporting or DSS Irregular or infrequent use
Do Not Use Prototyping If
Don’t understand toolsData not well managedSoftware not well managedProfessional staff not availableTechnology response not adequateUser not willing to invest time
Factors Favoring Prototyping
Structure: interactive, on-line (OLAP)Logic: structured but not algorithmic
DSS applications are often data-report types
User: competent and active participantTime Constraint: not a crash projectManagement: willing to work with methodSize: not overly large or complex
Factors Favoring Prototyping
Problem: imprecise specifications, poorly defined communications, interactive model needed
Why not use prototyping
Roles
User Responsible for business solutions
Intermediary Run system for userBuilder Write code for applicationTechnical Supports the development
Support toolsToolsmith Build basic tool modules (often
work for software houses)
Requirements for Successful Prototyping: User
Initiate the processSeeks IS assistanceCompetent in business areaWilling to spend time with system
Requirements for Successful Prototyping: Builder
Assigned to PrototypingCompetent with toolsKnows organizational data resources
Requirements for Successful Prototyping: Technology
Roles identified4GL Tools establishedData is managedTechnology response adequate
Builders Added Value(Professional Design)
Date and time stampsControl totalsAudit trailsCommon interface feelAdditional functionsTesting
Prototyping Principles
1. Most applications arise from a small set of basic systems
1. Batch edit/update 7. On-line application2. Batch reporting interface3. Batch data update 8. On-line report4. Batch interface5. On-line update/query6. On-line ad hoc query
Prototyping Principles
AddModifyDisplayDeleteLocate
BrowseActivateCopyConnectStop
2. Most systems use a common set of data processing functions
Prototyping Principles
3. Most editing derives from a small set of models.
Tunnel editsCross field editsCross record edits
Prototyping Principles
4. Most reports are based on a four step process.
Select data from the databaseSort by specificationFormat and edit for printingPrint
Prototyping Principles
Audit trailsControl totalsMenu and
command modesHelp facility
Standard screen formats
Date/time stamping
Ergonomics
5. There are a standard set of value added design structures that should be added
Prototyping Tactics
Normalize data to 3NFUse component engineering
Use existing componentsAssemble from existing partsReuse piecesCreate pieces so that they can be reused
Cut and pasteKeep a set of examples
Prototyping Tactics
Use active data dictionariesAutomate documentationKeep teams small Integrated software workbench toolsSpecify objectives not proceduresProvide end-user report writing toolsUse professional prototypersHave systems developers work with
prototypers
Project Management
Initial Model: 2-6 weeksMust be fast enough to maintain interest
Revisions: immediate - 2 weeksChargeback: use charges to avoid
frivolous changes Approval: determine the group who
approves iterationsSign off: formal acceptance
AdditionalImplementation RequirementsOperational documentation and
proceduresData size and operational impact
analysisTest planTraining procedures
Tactic
EvolutionThrowawayLife Cycle component
References
Bernard H. Boar, Application Prototyping, Wiley, 1984. Ralph Sprague & Eric Carlson, Building Effective Decision Support
Systems, Prentice Hall, 1984.