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 I Large Systems Intercommunications among applications Formal methodologies CASE technologies Purchased products Outsourcing

Type I SDLC Type I systems Large and Costly Cost justified Formal stages of evaluation Stages carefully reviewed and formally approved Data, Process, Communications

Type II Information 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 zPrespecification possible zChanges expensive zGood project communication zStatic model OK zRigorous approach useful zIteration unacceptable Prototype zPrespecification difficult zQuick tools work zCommunications gap zAnimated model needed zRigor after requirements zIteration accepted

The Prototyping Process Identify Initial Requirements Develop System Use and Evaluate Document and Install Iterate

Prototyping Life Cycle zDetermine suitability for prototyping zIdentify basic needs zDevelop working model zDemonstrate and solicit refinements zRevise and redemonstrate zClean up and document

Assumptions zAll requirements cannot be specified zQuick build tools are available zCommunications gap between builders and users zActive models are required zRigorous approaches are appropriate once requirements are known zIteration is valuable

Use Prototyping If zLife cycle too slow zScope of project manageable 30 screens Small team: 1-2 users/designers 50 attributes zUser not sure of specifications zUser satisfaction very important zReporting or DSS zIrregular or infrequent use

Do Not Use Prototyping If zDon’t understand tools zData not well managed zSoftware not well managed zProfessional staff not available zTechnology response not adequate zUser not willing to invest time

Factors Favoring Prototyping zStructure: interactive, on-line (OLAP) zLogic: structured but not algorithmic DSS applications are often data-report types zUser: competent and active participant zTime Constraint: not a crash project zManagement: willing to work with method zSize: not overly large or complex

Factors Favoring Prototyping zProblem: imprecise specifications, poorly defined communications, interactive model needed Why not use prototyping

Roles zUserResponsible for business solutions zIntermediaryRun system for user zBuilderWrite code for application zTechnicalSupports the development Supporttools zToolsmithBuild basic tool modules (often work for software houses)

Requirements for Successful Prototyping: User zInitiate the process zSeeks IS assistance zCompetent in business area zWilling to spend time with system

Requirements for Successful Prototyping: Builder zAssigned to Prototyping zCompetent with tools zKnows organizational data resources

Requirements for Successful Prototyping: Technology zRoles identified z4GL Tools established zData is managed zTechnology response adequate

Builders Added Value (Professional Design) zDate and time stamps zControl totals zAudit trails zCommon interface feel zAdditional functions zTesting

Prototyping Principles 1.Most applications arise from a small set of basic systems 1. Batch edit/update7. On-line application 2. Batch reporting interface 3. Batch data update8. On-line report 4. Batch interface 5. On-line update/query 6. On-line ad hoc query

Prototyping Principles zAdd zModify zDisplay zDelete zLocate zBrowse zActivate zCopy zConnect zStop 2. Most systems use a common set of data processing functions

Prototyping Principles 3. Most editing derives from a small set of models. zTunnel edits zCross field edits zCross record edits

Prototyping Principles 4. Most reports are based on a four step process. zSelect data from the database zSort by specification zFormat and edit for printing zPrint

Prototyping Principles zAudit trails zControl totals zMenu and command modes zHelp facility zStandard screen formats zDate/time stamping zErgonomics 5. There are a standard set of value added design structures that should be added

Prototyping Tactics zNormalize data to 3NF zUse component engineering Use existing components Assemble from existing parts Reuse pieces Create pieces so that they can be reused zCut and paste zKeep a set of examples

Prototyping Tactics zUse active data dictionaries zAutomate documentation zKeep teams small zIntegrated software workbench tools zSpecify objectives not procedures zProvide end-user report writing tools zUse professional prototypers zHave systems developers work with prototypers

Project Management zInitial Model: 2-6 weeks Must be fast enough to maintain interest zRevisions: immediate - 2 weeks zChargeback: use charges to avoid frivolous changes zApproval: determine the group who approves iterations zSign off: formal acceptance

Additional Implementation Requirements zOperational documentation and procedures zData size and operational impact analysis zTest plan zTraining procedures

Tactic zEvolution zThrowaway zLife Cycle component

References zBernard H. Boar, Application Prototyping, Wiley, zRalph Sprague & Eric Carlson, Building Effective Decision Support Systems, Prentice Hall, 1984.