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Systems Analysis
Transition to Systems Design
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Systems Analysis and Design Fourth Edition
Chapter 6
Transition to Systems Design
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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
Objectives
Discuss the systems design processand provide guidelines for system
design
Create and use appropriate codesduring systems design and
development
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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
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
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
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
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
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
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
Other software alternativesApplication service providers (ASP)
Outsourcing
End-user applications
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
Application service providersDelivers applications by charging a usage or
subscription fee
Service provided is called application hosting
Offer applications on a rental basis
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
OutsourcingUsing outside companies to handle portion of
the workload, on short-term or long-term basis
Contract personnel firms
Systems management or facilitiesmanagement firms
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
End-user systemsUtilizes standard business software
Can offer simple, low-cost solutions
Users can design their own data entry forms
and reports
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
Selecting a software alternativeDecision will affect remaining SDLC
phases
Systems analysts involvement dependson which alternative is selected
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
Evaluating Software Alternatives
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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
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
Steps in Evaluating andPurchasing Software Packages
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Systems Analysis and Design Fourth Edition
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
Steps in Evaluating andPurchasing Software Packages
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Systems Analysis and Design Fourth Edition
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
Steps in Evaluating andPurchasing Software Packages
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Systems Analysis and Design Fourth Edition
Step 4: make the purchaseSoftware licenses
Lease agreements
Maintenance agreements
Steps in Evaluating andPurchasing Software Packages
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Systems Analysis and Design Fourth Edition
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
Steps in Evaluating andPurchasing Software Packages
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Systems Analysis and Design Fourth Edition
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
Steps in Evaluating andPurchasing Software Packages
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Systems Analysis and Design Fourth Edition
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
Steps in Evaluating andPurchasing Software Packages
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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
Transition to Systems Design
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 Analysis and Design Fourth Edition
Transition to Systems Design
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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Transition to Systems Design
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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Systems Analysis and Design Fourth Edition
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
Overview of Systems Design
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Systems Analysis and Design Fourth Edition
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
Overview of Systems Design
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Systems Analysis and Design Fourth Edition
Overview of Systems Design
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 Analysis and Design Fourth Edition
Overview of Systems Design
Systems design considerationsProcessing considerations
Use a modular design
Design modules that perform a single function
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Systems Analysis and Design Fourth Edition
Overview of Systems Design
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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Systems Analysis and Design Fourth Edition
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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Systems Analysis and Design Fourth Edition
Designing and Using Codes
Types of CodingSequence codes
Block sequence codes
Alphabetic codesCategory codesAbbreviation codesMnemonic codes
Significant digit codes
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Systems Analysis and Design Fourth Edition
Designing and Using Codes
Types of codingSequence codes
Block sequence codes
Alphabetic codesCategory codesAbbreviation codesMnemonic codes
Significant digit codesDerivation codes
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Systems Analysis and Design Fourth Edition
Designing and Using Codes
Types of codingSequence codesBlock sequence codes
Alphabetic codes
Category codesAbbreviation codesMnemonic codes
Significant digit codesDerivation codesCipher codesAction codesSelf-checking codes
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Systems Analysis and Design Fourth Edition
Designing and Using Codes
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