Transcript Chapter 9: Information Systems Analysis and Design

IS Analysis & Design
Chapter 9
The Systems Development Life Cycle
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Overview
• Six phases of the SDLC
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First phase
Second phase
Third phase
Fourth phase
Fifth phase
Sixth phase
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Systems
• Collection of related components that
interact to perform a task in order to
accomplish a goal
• Computer-based information systems and
their interaction with the people of the
organization, its suppliers, and buyers
define the effectiveness and efficiency of
the systems
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System Review
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Marketing opportunities
Government regulations
New technology
Merger or acquisition with another
company
• Exponential changes in any portion of the
business process
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Formal Process
• Systems Development Life Cycle
– SDLC
• Formal assignment allows for milestones,
goals, and assessment
• Users play a vital role
– things are not all written or handled in an
intuitive way
– without adaptation, any new system is a failure
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User Participation in SDLC
• Current system methods
• Joint Application Development (JAD)
– analysts and users at equivalent levels work
together to define, discuss, suggest
improvement
• Explanation of departmental objectives and
requirements
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More User...
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Reports definition and format
Project approval and budgets
Evaluation and acceptance testing
Documentation and procedure
documentation
• Briefings and training sessions
– train the trainer
• Finally, user’s daily execution of
system
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System Failure
• The large majority of failures
are because system does not
define the way business is
conducted
• User requirements are not met
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Additional Reasons for Failure
• Lack of communication
• Continuing a project that should have been
cancelled
– like sunk costs in economics, a project should
not be continued based on the money spent
– a project should be continued based on the
expected revenue or benefit when the project is
completed
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More Failure Reasons
• System integration
• Technological incompetence
– the risk of failure in system implementation to a
large degree is based on the knowledge base of
the employees
• Major changes in middle of project
• Lack of user training
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Information Systems
• Money allocation for information systems
processing functions
– hardware
– software
– staff support
• Multiplicity of effort
– must coordinate full system - automated and
non-automated - goals and objectives
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Financial Outlay
• Not met users needs
• Unnecessary hardware
acquisition
• Insufficient hardware
• Software inadequately
tested
• Software performance
inadequate
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Phases
• Some phases are cross-life-cycle activities
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Fact-finding
Documentation and presentation
Estimation and measurement
Feasibility analysis
Project management
Process management
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Major Phases
• Preliminary
Investigation
• Systems analysis
• Systems design
• Systems development
• Systems
implementation
• Systems maintenance
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Who Participates?
• Users
• Management
– middle and upper
• Technical taff
• The less involvement,
the more likelihood of
failure
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SDLC
• Leader
– head systems analyst, systems engineer, or
project leader
• Use system approach
– complete, accurate, relevant, timely (CART)
• Often, a committee determines first step of
feasibility allowing the project funding and
execution
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Preliminary Investigation
‫ ٭‬Conduct preliminary
analysis
‫ ٭‬Propose alternative
solutions
‫ ٭‬Describe costs and
benefits
‫ ٭‬Submit preliminary
plan with
recommendations
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Preliminary Investigation
• Business Process Reengineering (BPR)
– redefines the fundamental business processes
• BPR
– independent of information technology
• Document nature and scope of the problems
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Propose Alternative Solutions
• Leave as is
– not justify
– part of a Electronic Data Interchange requiring
system conforming
• Improve the system
– upgrading
– retraining
• Develop a new system
– current computer system does not reflect or
properly support the business process
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Describe the Costs and Benefits
• Tangible
– actual dollar savings
– increase in system efficiency
• Intangible
– done for strategic competitive
advantages
– done for market share increase
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Preliminary Plan
• Written report submitted
• Includes major agreement by all three levels
of business
– transactional, middle management, strategic
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Detailed Systems Analysis
• Data gathering
– surveys, questionnaires, observations, random
and stratified sampling, structured and
unstructured interviews
• Data analyzing
– CASE (Computer-Aided Software Engineering
tools tie together dictionary/encyclopedia for
consistent use of terms, insure correct system
flow, data integrity, and report generation
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CASE
• Data dictionary
– encyclopedia or repository
• Data flow and system diagrams
– allows parallel processing beyond a data flow chart,
integrating the system being examined with the
entire enterprise
• Connectivity diagrams
– defines communications through networks
• Grid charts and decision tables ensure all cases
are met
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Systems Analysis
• Describes WHAT a
system is doing and what
it should do without
regard to HOW the
process is to be
accomplished
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OOA
• Object-oriented analysis
– instead of structured concerns in terms of
processes and data
– objects consisting of attributes and methods are
defined, more closely reflecting real-life
systems within an organization
– Software Engineering Institute has scientifically
proven that this methodology facilitates fewer
errors and less maintenance than structured
system designs
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Final Analysis Outcome
• Requirements
statement
– defines boundaries for
system design
– provides the basis for
testing scripts during
system implementation
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System Design
• Preliminary design
– general functional capabilities
– further definition through prototyping
with user input
• Detailed design
– input and output requirements
– processing and system controls
– backup and contingency designs
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CASE in Systems Design
• Front-end, or upper CASE
– used for preliminary investigation,
analysis and design
• Back-end, or lower CASE
– systems development and
implementation
– coding and testing support future
maintenance testing and proofs of
correctness
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Project Management
• Determines resources of people and systems
• Maps out interaction to resolve conflicts
and bottlenecks
• Running project management software does
not in itself create project management
– it is the act of examining and changing project
software that creates the management
• Includes Gantt and PERT charts
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Gantt and PERT charts
• Gantt shows bar chart diagrams
– used for upper management to
simply showing project progress
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PERT
• Program Evaluation and Review Technique
– shows timing and relationship
– clearly show critical path, where delays in the
project will slow total completion time
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Detailed Design
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Output requirements
Input requirements
Storage requirements
Processing and network
requirements
• System controls and backup
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Final Design Output
• Design specifications
• Including continuing
feasibility analysis
– economic, technical, and
operational
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System Development
• Acquisition of
software/hardware
– make and/or buy
• Development of software
– customization of shrink-wrap
software
• Unit testing
• System testing
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System Implementation
• Conversion
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facilities
hardware
database
software
• Direct, parallel, phased, or pilot
– rarely are business or financial
institutions employing direct because
of accountability issues
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Finally in Implementation
• Completed
documentation
– integrated on and off-line
• Train the users
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System Maintenance
• Auditing
• Evaluation
• Types of maintenance
– perfective
– corrective
– enhancement
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