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Transition to Systems Design. Systems Analysis. Chapter 6. Transition to Systems Design. Objectives. Evaluate software alternatives and development strategies Explain advantages and disadvantages of developing in-house software versus purchasing and customizing a software package

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chapter 6
Chapter 6

Transition to Systems Design

Systems Analysis and Design Fourth Edition

objectives
Objectives
  • Evaluate software alternatives and development strategies
  • Explain advantages and disadvantages of developing in-house software versus purchasing and customizing a software package
  • Describe how companies use out-sourcing and user applications

Systems Analysis and Design Fourth Edition

objectives4
Objectives
  • List the steps in purchasing and evaluating a software package
  • Explain the differences between a request for proposal (RFP) and a request for quotation (RFQ)
  • Describe the system requirements document and the presentation to management at the end of the systems analysis phase

Systems Analysis and Design Fourth Edition

objectives5
Objectives
  • Explain the transition from systems analysis to systems design, and the difference between logical and physical design
  • Explain the importance of prototyping and describe various prototyping methods, tools, and techniques

Systems Analysis and Design Fourth Edition

objectives6
Objectives
  • Discuss the systems design process and provide guidelines for system design
  • Create and use appropriate codes during systems design and development

Systems Analysis and Design Fourth Edition

introduction
Chapter 6 covers the remaining tasks in the systems analysis phase

Evaluation of alternative solutions

Preparation of the system requirements document

Presentation to management

Introduction

Systems Analysis and Design Fourth Edition

evaluating software alternatives
Make or buy decision

In-house software

Developed by the company’s IS department

Software package

Purchased or leased from software publishers or vendors

Horizontal application

Vertical application

Evaluating Software Alternatives

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Developing software in-house

Reasons for in-house development

Satisfy unique requirements

Minimize changes in business procedures and policies

Meet constraints of existing systems

Meet constraints of existing technology

Develop internal resources and capabilities

Evaluating Software Alternatives

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Purchasing a software package

Reasons for purchasing a software package

Lower costs

Less time to implement

Proven reliability and performance benchmarks

Less technical development staff

Future upgrades provided by the vendor

Other companies as resources

Evaluating Software Alternatives

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Customizing Software packages

Purchase a basic package that can be customized to suit your needs

Negotiate with software vendor to make enhancements to suit your needs

Purchase the package and make your own modifications

Evaluating Software Alternatives

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Other software alternatives

Application service providers (ASP)

Outsourcing

End-user applications

Evaluating Software Alternatives

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Application service providers

Delivers 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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Outsourcing

Using outside companies to handle portion of the workload, on short-term or long-term basis

Contract personnel firms

Systems management or facilities management firms

Evaluating Software Alternatives

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End-user systems

Utilizes 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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Selecting a software alternative

Decision will affect remaining SDLC phases

Systems analyst’s involvement depends on which alternative is selected

Evaluating Software Alternatives

Systems Analysis and Design Fourth Edition

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Evaluating Software Alternatives

Systems Analysis and Design Fourth Edition

steps in evaluating and purchasing software packages
Five step process

1. Evaluate the information system requirements

2. Identify potential software vendors

3. Evaluate software package alternatives

4. Make the purchase

5. Install the software package

Steps in Evaluating and Purchasing Software Packages

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Step 1: evaluate the information system requirements

Identify the key features of the system

Estimate volume and future growth

Specify any hardware constraints

Prepare a request for proposal or quotation

Steps in Evaluating and Purchasing Software Packages

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Step 2: identify potential software vendors

Next step is to contact potential vendors

An RFP will help vendors to identify solutions

Various sources of information on suppliers

Retailers

Computer manufacturers

Industry trade journals or Web sites

IT consultants

Newsgroups

Steps in Evaluating and Purchasing Software Packages

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Step 3: evaluate software package alternatives

Object is to compare software packages and select the best alternative

Obtain information from many sources

Evaluation process

Obtain information from existing users

Test the application

Benchmark the package if necessary

Steps in Evaluating and Purchasing Software Packages

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Step 4: make the purchase

Software licenses

Lease agreements

Maintenance agreements

Steps in Evaluating and Purchasing Software Packages

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Step 5: install the software package

Installation time depends on size and complexity

Before using the package, complete all implementation steps

Loading, configuring, and testing the software

Training users

Converting data files to new format

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Evaluation and selection teams

Objective of the process is to obtain the product with the lowest cost of ownership

Team approach ensures that critical factors are not overlooked and that a sound choice is made

Steps in Evaluating and Purchasing Software Packages

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Evaluation and selection teams

Primary 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 and Purchasing Software Packages

Systems Analysis and Design Fourth Edition

completion of systems analysis
System requirements document

Also called software requirements specification

Describes alternatives and makes recommendation 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 management

Five probable management decisions

1. Develop an in-house system

2. Modify the current system

3. Purchase or customize a software package

4. Perform additional systems analysis work

5. Stop all further work

Completion of Systems Analysis

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Transition to Systems Design
  • Essential to have an accurate and understandable system requirements document
  • Errors, omissions, and ambiguities will affect the quality of the finished product

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Transition to Systems Design
  • Systems design overview
    • Logical 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 analysis and design
    • Design phase cannot begin until analysis work is complete
    • Should return to the analysis phase only in very limited situations

Systems Analysis and Design Fourth Edition

overview of systems design
Analysts must understand entire logical design before beginning physical design

Systems design steps

Review the system requirements

Design the system

Output

Input

Files and databases

System architecture

Present the systems design

Overview of Systems Design

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Systems design objectives

Build a system that is:

Effective

Reliable

Maintainable

Overview of Systems Design

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Systems design considerations

User considerations

Make the system user-friendly

Consider where users receive output, or provide input to the system

Anticipate future needs

Users

Information system

Organization

Must provide flexibility

Overview of Systems Design

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Overview of Systems Design
  • Systems design considerations
    • Data 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 once
      • Avoid data duplication

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Overview of Systems Design
  • Systems design considerations
    • Processing considerations
      • Use a modular design
      • Design modules that perform a single function

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Overview of Systems Design
  • Design tradeoffs
    • Design goals often conflict with each other
      • Easier use might create more complex programming requirements
      • More flexibility might increase maintenance needed
      • Meeting one user’s requirements might make it harder to satisfy another’s needs
    • A major issue is quality versus cost

Systems Analysis and Design Fourth Edition

designing and using codes
Designing and Using Codes
  • A code is a set of letters or numbers that represents an item of data
  • Overview of codes
    • Codes serve many useful purposes
      • Save 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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Designing and Using Codes
  • Types of coding
    • Sequence codes
    • Block sequence codes
    • Alphabetic codes
      • Category codes
      • Abbreviation codes
        • Mnemonic codes

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Designing and Using Codes
  • Types of Coding
    • Sequence codes
    • Block sequence codes
    • Alphabetic codes
      • Category codes
      • Abbreviation codes
        • Mnemonic codes
    • Significant digit codes

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Designing and Using Codes
  • Types of coding
    • Sequence codes
    • Block sequence codes
    • Alphabetic codes
      • Category codes
      • Abbreviation codes
        • Mnemonic codes
    • Significant digit codes
    • Derivation codes

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Designing and Using Codes
  • Types of coding
    • Sequence codes
    • Block sequence codes
    • Alphabetic codes
      • Category codes
      • Abbreviation codes
        • Mnemonic codes
    • Significant digit codes
    • Derivation codes
    • Cipher codes
    • Action codes
    • Self-checking codes

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Designing and Using Codes
  • Developing a code
    • Keep codes concise
    • Allow for expansion
    • Keep codes stable
    • Makes codes unique
    • Use sortable codes
    • Avoid confusing codes
    • Make codes meaningful
    • Use a code for a single purpose
    • Keep codes consistent

Systems Analysis and Design Fourth Edition