Ch. 13 Systems Design, Implementation, Maintenance, and Review

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Ch. 13 Systems Design, Implementation,
Maintenance, and Review

• System Design
• The purpose to describe how the information
  system will function to meet its requirements.
• Main deliverable a technical specification
  document that details system outputs, inputs,
  interfaces, hardware, software, databases,
  telecommunications, personnel, and procedures.
• Design stage logical and physical design

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Logical Design

• Produces a description of what the system must do
  (the functional requirements)
• Output design types, format, content, frequency
• Input design types, format, content, frequency
• Processing design calculations, comparisons,
  manipulations
• File database design capabilities and
  organization
• Telecommunications design high-level network
  description
• Procedures design automated manual
• Controls security design
• Personnel job design

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Physical Design

• Describes the technology or other components
  needed to complete the logical design.
• Hardware design
• Software design
• Database design
• Telecommunications design
• Personnel design
• Procedures controls design

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Special System Design Considerations

• Sign-on procedures
• Consists of identification numbers or names,
  passwords, and other procedures needed to access
  system resources
• Interactive processing
• Interactive dialog
• The messages and prompts communicated between a
  user and a computer
• Preventing, detecting, and correcting errors

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A full-screen menu interface
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Pull-down Menu
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Forms dialog boxes
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Emergency Alternate Procedures Disaster Recovery

• Telecommunications backup
• Personnel backup
• Hardware backup
• Disaster recovery plans
• Hot site
• Cold site (Shells)
• Software database backup
• Selective backups
• Incremental backups
• Image log

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System Controls

• Deterrence controls
• designed to prevent problems by physically
  excluding unauthorized personnel from operating
  computers
• involve having a closed shop, where only
  specifically authorized operators can enter and
  run the computers.
• Input controls sign-on procedures checking
  input
• Processing controls backup procedures
• Output controls
• Database controls Passwords and user views
• Telecommunications controls Use of encryption
• Personnel controls Logins, passwords, ID badges,
  or smart cards

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Systems Design Alternatives

• A request for proposal (RFP)
• Formally describes the hardware, software or
  services needed as well as the time frame, and
  requests bids.
• Acquisition options
• Renting (Short-term option)
• appropriate for an application that is rapidly
  changing or when a company wants to try out a
  particular kind of software
• Leasing (longer-term option)
• Purchasing may provide a lower cost over the
  long run, but a company runs the risk of having a
  big investment in obsolete technology.

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Evaluating and selecting a system design

• Preliminary evaluation
• An initial assessment whose purpose is to dismiss
  unwanted proposals
• Final evaluation,
• A detailed investigation of the proposals offered
  by the vendors remaining after the preliminary
  evaluation
• Evaluation Techniques
• Group consensus
• Cost/benefit analysis
• Benchmark test
• Point evaluation

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Fig 13.4
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Table 13.4
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Fig 13.5
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Fig 13.6
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The Design Report

• contains the system specifications, and is the
  primary output of the design stage.
• This includes technical descriptions of system
  inputs, outputs, interfaces, hardware, software,
  databases, telecommunications, personnel and
  procedures.

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System implementation

• includes hardware acquisition, software
  acquisition or development, user preparation,
  hiring training personnel, site preparation,
  data preparation, installation, testing, start-up
  and user acceptance.
• Acquiring hardware
• Hardware can be purchased, leased or rented.
  Application service providers can not only
  provide software, but also the hardware and end
  user support.

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Acquiring software Make or Buy?

• Externally developed software
• Lower cost
• Lower risk
• Ease of installation
• Steps
• Review needs requirements
• Acquire software
• Modify customize
• Acquire software interfaces
• Test accept the software
• Maintain the software

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Make or Buy Software

• In-house developed software
• Chief programmer teams
• a group of IS professionals with total
  responsibility for designing and implementing an
  information system
• The programming life cycle
• Language selection
• Program coding
• Testing and debugging
• Documentation
• Implementation (Conversion)

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Tools Techniques for Software Development

• Structured design
• Structured programming
• Structured walkthroughs
• Cross-platform development
• Integrated development environments
• CASE tools

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Structured Design

• breaks larger problems into individual modules
• Structured Programming
• improves the logical program flow by grouping
  program instructions according to their function
• Sequence structure
• Decision structure
• Loop structure
• Top-Down approach
• developing the main module first, then developing
  the next modules executed, then the next, and so
  on

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Structured Programming

• Start with a structured analysis
• Develop a modular design
• Top-down design
• Write procedural programs
• combination of three control structures
• sequence, selection, and repetition.

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Modular Programming

• Divide software tasks into modules
• Allows programming teams to work independently
• Isolates debugging

Shipping Module
Order Taking Module
Customer Information Retrieval
Inventory Control
Credit Check
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Fig 13.11
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Fig 13.12
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Structured Walkthroughs

• A step-by-step review of any deliverable
  throughout the development process to identify
  errors.
• Team members review the progress and evaluate the
  item being reviewed

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Other techniques and tools

• Cross-platform development
• Allows programmers to develop programs that can
  run on computer systems having different hardware
  and operating systems, or platforms
• Integrated Development Environments (IDEs)
• Software that combines the tools needed for
  programming with a programming language into one
  integrated package
• CASE Tools

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Additional Implementation Activities

• Acquiring database and telecommunication systems
• User preparation
• Hiring training IS personnel
• Site preparation
• preparation of the location of the new system
• Data preparation (Data conversion)
• Conversion of manual files into computer files
• Installation
• The process of physically placing the computer
  equipment on the site and making it operational

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Additional Implementation Activities- Testing

• Unit testing
• Testing of individual programs
• System testing
• Testing the entire system of programs
• Volume testing
• Testing the application with a large amount of
  data
• Integration testing
• Testing all related systems together
• Acceptance testing
• Conducting any tests required by the user

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Additional Implementation Activities- Start-Up

• Direct conversion (plunge or direct cutover)
• involves completely stopping the old system and
  starting the new system on a given date.
• Phase-in approach
• components of the old system are slowly replaced
  by components of the new system, application by
  application
• Pilot start-up
• installing the system for one group of users
• Parallel start-up
• both the old and new systems are run concurrently
  until it is clear that all the problems have been
  worked out of the new system

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System Maintenance

• involves monitoring, changing, fixing and
  enhancing an operational information system
• Reasons for Maintenance
• Changes in business processes
• Requests from stakeholders, users, or managers
• Errors in the program
• Technical hardware problems
• Corporate mergers acquisitions
• Government regulations
• Changes in the operating system or hardware

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Types of maintenance

• Slipstream upgrade
• Minor upgrade that isnt worth announcing
• Involves fixing a minor problem or bug, then
  recompiling the code
• Patch
• Corrects a problem or enhances the program by an
  addition to the program
• Release
• Requires changes in the software documentation
• Version
• a major program change, introducing new features
  and eliminating or changing existing features.

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Systems Review

• the process of analyzing systems to determine
  whether or not they are operating as intended.
• Actual system performance and benefits are
  compared to the system requirements, and cost,
  control, and complexity factors are re-examined.
  
• When problems or shortcomings are found,
  maintenance to the system is requested.
• Systems review is an ongoing process, continuing
  throughout a systems life.

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Types of Review Procedures

• Event-driven review
• Triggered by an occurrence-
• A problem with an existing system
• A merger
• A user request
• Time-driven review
• Occur as a mater of time
• Monthly review
• Yearly review
• Five-year review

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Factors to Consider During Systems Review

• Mission
• Goals
• Hardware/ software
• Database
• Telecommunications
• IS personnel
• Control

• Training
• Costs
• Complexity
• Reliability
• Efficiency
• Response time
• Documentation