Transcript Document 7518376

• Designing new systems or modifying existing ones should
always be aimed at helping an organization achieve its goals
• State the purpose of systems design and discuss the differences
between logical and physical systems design
• Describe some considerations in design modeling and the diagrams
used during object-oriented design
• Outline key considerations in interface design and control and
system security and control.
• Define the term RFP and discuss how this document is used to drive
the acquisition of hardware and software.
• Describe the techniques used to make systems selection evaluations
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• The primary emphasis of systems implementation is to
make sure that the right information is delivered to the right
person in the right format at the right time
• State the purpose of systems implementation and discuss the
various activities associated with this phase of systems
development
• List the advantages and disadvantages of purchasing versus
developing software
• Discuss the software development process and some of the tools
used in this process, including object-oriented program
development tools
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• Maintenance and review add to the useful life of a system but
can consume large amounts of resources. These activities
can benefit from the same rigorous methods and project
management techniques applied to systems development.
• State the importance of systems and software
maintenance and discuss the activities involved
• Describe the systems review process
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Systems Design
• Answers the question “How will the information system
do what it must do to solve a problem?”
• Has two dimensions: logical and physical
• Logical design: description of the functional
requirements of a system
• Physical design: specification of the characteristics of the
system components necessary to put the logical design
into action
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Logical Design
• Output requirements
• Input requirements
• Process requirements
• File and database requirements
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Logical Design (continued)
• Telecommunications requirements
• Procedure requirements
• Controls and security requirements
• Personnel and job requirements
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Physical Design
• Hardware specifications
• Software specifications
• Database specifications
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Physical Design (continued)
• Telecommunications specifications
• Personnel specifications
• Procedure and control specifications
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Object-Oriented Design
• Design key objects and classes of objects in the new or
updated system
• Consideration of the problem domain, the operating
environment, and the user interface
• Consideration of the sequence of events that must happen
for the system to function correctly
• A sequence of events is often called a scenario
• A scenario can be diagrammed in a sequence diagram
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Figure 13.4: The Levels of the Sign-On
Procedure
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Interface Design and Controls
(continued)
• Interactive processing
• Menu-driven systems
• Help commands
• Table lookup facilities
• Restart procedures
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Table 13.1: The Elements of Good
Interactive Dialogue
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Design of System Security and
Controls
• Preventing, detecting, and correcting errors
• Disaster planning and recovery
• Disaster planning: the process of anticipating and
providing for disasters
• Disaster recovery: the implementation of the disaster plan
• Hardware backup
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Design of System Security and
Controls (continued)
• Disaster planning and recovery (continued)
• Software and database backup
• Telecommunications backup
• Personnel backup
• Systems controls: rules and procedures to maintain data
security
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Generating Systems Design
Alternatives
• Request for proposal (RFP): a document that specifies
in detail required resources such as hardware and
software
• Financial options
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Evaluating and Selecting a Systems
Design
• Preliminary evaluation
• To dismiss the unwanted proposals
• Begins after all proposals have been submitted
• Final evaluation
• A detailed investigation of the proposals offered by the
vendors remaining after the preliminary evaluation
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Figure 13.7: The Stages in Preliminary
and Final Evaluations
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Evaluation Techniques
• Group consensus
• Cost/benefit analysis
• Benchmark tests
• Point evaluation
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Figure 13.8: An Illustration of the Point
Evaluation System
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Figure 13.9: Freezing Design
Specifications
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The Design Report
• Primary result of systems design
• Reflects the decisions made and prepares the way for
systems implementation
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Figure 13.11: Typical Steps in Systems
Implementation
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Acquiring Hardware from an IS Vendor
• An IS vendor is a company that offers hardware,
software, telecommunications systems, databases, IS
personnel, and/or other computer-related resources
• Buying computer hardware
• Leasing computer hardware
• Renting computer hardware
• “Pay-as-you-go,” “on-demand,” or “utility” computing
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Acquiring Software: Make or Buy?
• Externally developed software: lower cost, lower risk,
ease of installation
• In-house developed software
• Meeting user and organizational requirements
• More features and increased flexibility in terms of
customization and changes
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Acquiring Software: Make or Buy?
(continued)
• In-house developed software (continued)
• Greater potential for providing a competitive advantage
• Chief programmer teams
• The programming life cycle
• Tools and techniques for software development
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Figure 13.13: Steps in the
Programming Life Cycle
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Tools and Techniques for Software
Development
• Structured programming
• Improving the logical program flow by breaking the
program into groups of statements, called structures
• CASE tools: used during software development to
automate some of the techniques
• Object-oriented implementation
• A collection of existing modules of code, or objects, can be
used across a number of applications
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Tools and Techniques for Software
Development (continued)
• Cross-platform development: allows programmers to
develop programs that can run on computer systems
having different hardware and operating systems, or
platforms
• Integrated development environment: combines the
tools needed for programming with a programming
language into one integrated package
• Structured walkthrough: a planned and preannounced
review of the progress of a program module, a structure
chart, or a human procedure
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Acquiring Database and
Telecommunications Systems
• Relational databases
• Object-oriented database systems
• Databases are a blend of hardware and software
• Telecommunications systems require a blend of hardware
and software
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User Preparation
• Readying managers, decision makers, employees, other
users, and stakeholders for new systems
• Training users
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IS Personnel: Hiring and Training
• IS manager
• Systems analysts
• Computer programmers
• Data-entry operators
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Site Preparation
• Preparation of the location of a new system
• Making room for a computer in an office
• Special wiring and air conditioning
• Special floor
• Additional power circuits
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Data Preparation
• Also called data conversion
• Ensuring all files and databases are ready to be used with
new computer software and systems
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Installation
• The process of physically placing the computer
equipment on the site and making it operational
• Normally the manufacturer is responsible for installing
computer equipment
• Someone from the organization (usually the IS manager)
should oversee the process
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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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Start-Up
• The process of making the final tested information system
fully operational
• Direct conversion (also called plunge or direct cutover)
• Phase-in approach
• Pilot start-up
• Parallel start-up
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User Acceptance
• User acceptance document: formal agreement signed by
the user that states that a phase of the installation or the
complete system is approved
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Systems Operation and Maintenance
• Systems operation: use of a new or modified system
• Systems maintenance: checking, changing, and
enhancing the system to make it more useful in achieving
user and organizational goals
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Types of Maintenance
• Slipstream upgrade
• Patch
• Release
• Version
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Figure 13.19: Maintenance Costs as a
Function of Age
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Figure 13.20: The Value of Investment
in Design
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Systems Review
• Process of analyzing systems to make sure that they are
operating as intended
• Often compares the performance and benefits of the
system as it was designed with the actual performance
and benefits of the system in operation
• Event-driven review: review triggered by a problem or
opportunity such as an error, a corporate merger, or a new
market for products
• Time-driven review: review performed after a specified
amount of time
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Factors to Consider During Systems
Review
• Mission
• Organizational goals
• Hardware and software
• Database
• Telecommunications
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Factors to Consider During Systems
Review (continued)
• Information systems personnel
• Control
• Training
• Costs
• Complexity
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Factors to Consider During Systems
Review (continued)
• Reliability
• Efficiency
• Response time
• Documentation
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Summary
• Systems design answers the question “How will the
information system do what it must do to solve a
problem?”
• Systems design has two dimensions: logical and physical
• Logical design is description of the functional
requirements of a system
• Physical design is specification of the characteristics of
the system components necessary to put the logical design
into action
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Summary (continued)
• Steps of systems implementation: hardware acquisition,
software acquisition, user preparation, personnel: hiring
and training, site preparation, data preparation,
installation, testing, start-up, and user acceptance
• Systems operation is the use of a new or modified system
• Systems maintenance involves checking, changing, and
enhancing the system to make it more useful in achieving
user and organizational goals
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Summary (continued)
• Systems review is the process of analyzing systems to
make sure that they are operating as intended
• Event-driven review is triggered by a problem or
opportunity such as an error, a corporate merger, or a new
market for products
• Time-driven review is performed after a specified amount
of time
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