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Systems Analysis

Transition to Systems Design

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Systems Analysis and Design Fourth Edition

Chapter 6


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Objectives

Evaluate software alternatives anddevelopment strategies

Explain advantages and

disadvantages of developing in-housesoftware versus purchasing and

customizing a software package

Describe how companies use out-sourcing and user applications

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Objectives

List the steps in purchasing andevaluating a software package

Explain the differences between a

request for proposal (RFP) and arequest for quotation (RFQ)

Describe the system requirements

document and the presentation tomanagement at the end of the

systems analysis phase

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Objectives

Explain the transition from systemsanalysis to systems design, and the

difference between logical and

physical designExplain the importance of prototyping

and describe various prototyping

methods, tools, and techniques

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Objectives

Discuss the systems design processand provide guidelines for system

design

Create and use appropriate codesduring systems design and

development

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Chapter 6 covers the remaining tasksin the systems analysis phase

Evaluation of alternative solutions

Preparation of the system requirementsdocument

Presentation to management

Introduction

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Make or buy decisionIn-house software

Developed by the companys IS department

Software packagePurchased or leased from software publishers

or vendors

Horizontal application

Vertical application

Evaluating Software Alternatives

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Developing software in-houseReasons for in-house development

Satisfy unique requirements

Minimize changes in business procedures andpolicies

Meet constraints of existing systems

Meet constraints of existing technology

Develop internal resources and capabilities


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Purchasing a software packageReasons for purchasing a software

package

Lower costs

Less time to implement

Proven reliability and performance

benchmarks

Less technical development staffFuture upgrades provided by the vendor

Other companies as resources


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Customizing Software packagesPurchase a basic package that can be

customized to suit your needs

Negotiate with software vendor to makeenhancements to suit your needs

Purchase the package and make your

own modifications


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Other software alternativesApplication service providers (ASP)

Outsourcing

End-user applications


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Application service providersDelivers applications by charging a usage or

subscription fee

Service provided is called application hosting

Offer applications on a rental basis


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OutsourcingUsing outside companies to handle portion of

the workload, on short-term or long-term basis

Contract personnel firms

Systems management or facilitiesmanagement firms


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End-user systemsUtilizes standard business software

Can offer simple, low-cost solutions

Users can design their own data entry forms

and reports


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Selecting a software alternativeDecision will affect remaining SDLC

phases

Systems analysts involvement dependson which alternative is selected


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Five step process1. Evaluate the information system

requirements

2. Identify potential software vendors3. Evaluate software package

alternatives

4. Make the purchase5. Install the software package

Steps in Evaluating andPurchasing Software Packages

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Step 1: evaluate the information systemrequirements

Identify the key features of the system

Estimate volume and future growthSpecify any hardware constraints

Prepare a request for proposal or

quotation


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Step 2: identify potential softwarevendorsNext step is to contact potential vendorsAn RFP will help vendors to identify

solutionsVarious sources of information on

suppliersRetailersComputer manufacturersIndustry trade journals or Web sitesIT consultantsNewsgroups


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Step 3: evaluate software packagealternatives

Object is to compare software packages

and select the best alternativeObtain information from many sources

Evaluation process

Obtain information from existing users

Test the application

Benchmark the package if necessary


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Step 4: make the purchaseSoftware licenses

Lease agreements

Maintenance agreements


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Step 5: install the software packageInstallation time depends on size and

complexity

Before using the package, complete allimplementation steps

Loading, configuring, and testing the software

Training users

Converting data files to new format


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Evaluation and selection teamsObjective of the process is to obtain the

product with the lowest cost of ownership

Team approach ensures that criticalfactors are not overlooked and that a

sound choice is made


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Evaluation and selection teamsPrimary objectives

Eliminate system alternatives that will not

work

Rank the alternatives that will work

Present the viable alternatives to management

for a final decision


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System requirements documentAlso called software requirements

specification

Describes alternatives and makesrecommendation to management

Similar to a contract for what will be

delivered

Must be clear and understandable to

users

Completion of Systems Analysis

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Presentation to managementFive probable management decisions

1. Develop an in-house system

2. Modify the current system3. Purchase or customize a

software package

4. Perform additional systemsanalysis work

5. Stop all further work

Completion of Systems Analysis

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Essential to have an accurate andunderstandable system requirements

document

Errors, omissions, and ambiguities willaffect the quality of the finished

product

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Systems design overviewLogical design defines the functions and

features of the system

Also know as the essential model

Physical design is a plan for the

implementation of the system

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The relationship between analysisand design

Design phase cannot begin until analysis

work is completeShould return to the analysis phase only

in very limited situations

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Analysts must understand entirelogical design before beginningphysical design

Systems design stepsReview the system requirements

Design the systemOutput

InputFiles and databases

System architecture

Present the systems design

Overview of Systems Design

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Systems design objectivesBuild a system that is:EffectiveReliable

Maintainable


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Systems design considerationsUser considerationsMake the system user-friendly

Consider where users receive output, or

provide input to the systemAnticipate future needs

Users

Information system

OrganizationMust provide flexibility


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Systems design considerationsData considerations

Enter data where and when it occurs

Verify data where it is input

Use automated data-entry methods

Control access for data entry

Report all entries or changes to critical values

Enter data into a system only onceAvoid data duplication

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Systems design considerationsProcessing considerations

Use a modular design

Design modules that perform a single function

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Design tradeoffsDesign goals often conflict with each

other

Easier use might create more complex

programming requirements

More flexibility might increase maintenance

needed

Meeting one users requirements might make

it harder to satisfy anothers needs

A major issue is quality versus cost

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Designing and Using Codes

A code is a set of letters or numbersthat represents an item of data

Overview of codes

Codes serve many useful purposesSave storage space and costs

Reduce data transmission time

Decrease data entry time

Can reveal or conceal information

Can reduce input errors

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Types of CodingSequence codes

Block sequence codes

Alphabetic codesCategory codesAbbreviation codesMnemonic codes

Significant digit codes

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Types of codingSequence codes

Block sequence codes

Alphabetic codesCategory codesAbbreviation codesMnemonic codes

Significant digit codesDerivation codes

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Types of codingSequence codesBlock sequence codes

Alphabetic codes

Category codesAbbreviation codesMnemonic codes

Significant digit codesDerivation codesCipher codesAction codesSelf-checking codes

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Developing a codeKeep codes conciseAllow for expansionKeep codes stable

Makes codes uniqueUse sortable codesAvoid confusing codesMake codes meaningfulUse a code for a single purposeKeep codes consistent

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EndChapter 6

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CHAP06r1