Systems Analysis and Design

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Systems Analysis and Design IT 1402
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Today's Lesson

• System Development Life Cycle
• Why we need a SDLC
• Advantages of using and SDLC
• The Waterfall Model
• Spiral Model
• Lifecycle vs. Methodology
• Methodology

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Why we need a SDLC

• Ease the process of building a system
• Avoid development problems
• Unclear objectives
• Cost overruns
• Development delays
• Avoid the system not meeting user requirements

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Advantages of a Life Cycle

• Facilitate project review
• Provide a more efficient / effective system
• Guide the systems development
• Improve communications
• Improve management and control
• Computer-based support

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Waterfall Model
Problem Definition
Requirement Analysis
System Design
System Development
System Testing
Maintenance
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Problem Definition

• Project Goals
• A broad statement of What the user expects from
  the system
• Project Bounds
• What areas the system effects and what areas
  remain the same
• Project Limits
• Resource limits (Financial, technology, human,
  S/w, H/w)

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Requirement Analysis

• The current system
• What it does, and how it works
• A Detail Model in subject terms
• What the new system will do, how it will work
• High level description of the system

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System Design

• Produce a detailed specification for the new
  system
• Here the description of the system analysis is
  converted in to a design which can be implemented

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Steps in System Design

• Select equipment
• Specify new programs or changes to existing
  programs
• Specify new database or changes to existing
  database
• Produce detailed procedures (Detailed Design)

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System Development

• The Detailed design is converted into the system
• Individual system components are built and tested
• Data and tools are used to build the system
• User interfaces are developed and tried by users
• Database is initialized with data

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System Testing

• Two phases in testing
• Unit testing (Individual components are tested)
• Integrated testing (The interfaces between these
  components are tested)
• Test and evaluate results

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Implementation and Maintenance

• Installation of the system at the client end
• Eliminate errors in the system during its working
  life.
• Fixing any bugs and problem found by users
• Tune the system to any variations in its working
  environment

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Problems with the Waterfall Model

• Rigid design and inflexible procedure
• Top-down procedure
• Real projects rarely follow the sequential flow
  that the model proposes
• One phase must be completed before the next phase
  starts
• At the beginning of most projects there is often
  a great deal of uncertainty about requirements
  and goals, and it is therefore difficult for
  customers to identify these criteria on a
  detailed level. The model does not accommodate
  this natural uncertainty very well.

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Problems with the Waterfall Model

• No phase can be repeated
• Assumptions made in the early phases no longer
  hold
• Some of the early work is incomplete
• Something was overlooked or not completely
  understood.

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The Modified Waterfall Model
Problem Definition
Requirement Analysis
System Design
System Development
System Testing
Maintenance
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Spiral Model
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Main phases in the Spiral Model

• Requirement analysis
• Design prototype
• Develop and integrate
• Acceptances and testing

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Life Cycle vs. Methodology

• The software development process consists of
  several well-defined steps.
• When following a design methodology, a designer
  can select appropriate modeling method related to
  each step

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Life Cycle vs. Methodology

• A system life cycle
• divides the life of an
• information system
• into two major
• Stages
• Systems Development
• Systems operation and support.

LIFE CYCLE STAGE System Operation
Support Using Information Technology
LIFE CYCLE STAGE System Development Using
System Development Methodologies
Lifetime Of a System
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Life Cycle vs. Methodology

• A system development methodology is a very formal
  and precise system development process that
  defines
• A set of activities
• Methods
• Best practices
• Deliverables
• Automated tools

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System Development methodology

• A System Development methodology (Process) has
  some general principles.
• P1 Get the owner and User Involved
• P2 Use a problem-solving approach
• Study and understand the problem and its context
• Define the requirement of a suitable solution.
• Identify candidate solutions and select the best
  solution.
• Design and/or implement the solution.
• Observe and evaluate the solutions impact, and
  refine the solution accordingly

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System Development methodology

• P3 Establish phases and activities
• Preliminary investigation
• Problem analysis
• Requirement analysis
• Decision analysis
• Design
• Construction
• Implementation

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System Development methodology

• P4 Establish standards
• Documentation
• Quality
• Automated Tools
• Information technology

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System Development methodology

• P5 Justify systems as capital investments
• Cost effectiveness
• Risk management

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System Development methodology

• P6 Dont be afraid to cancel or revise scope
• Cancel the project if it is no longer feasible
• If project scope is to be increased, reevaluate
  and adjust the cost and schedule
• If the project budget and schedule are frozen and
  not sufficient to cover all project objectives,
  reduce the scope

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System development methodology

• P7 Divide and conquer
• We divide a system into subsystem and components
• Easily to conquer the problem
• Easy to build a large problem

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System Development methodology

• P8 Design systems for growth and change
• Correcting simple mistakes
• To redesigning the system to accommodate changing
  technology
• To making modification to support changing user
  requirements.

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Development Process

• Methodology
• Modeling Methods or Techniques
• Tools

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Methodology

• Provides the framework
• Has a predefined set of steps
• Ensures that systems are built in the most
  effective way
• Uses tools and modeling methods

E.g. SSADM, RUP
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Modeling Methods

• A set of techniques used to implement a
  Methodology
• Data Flow Diagrams
• Entity Relationship Diagrams
• Structure Charts etc.

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System Development methodologies

• Supported by Modeling Methods or Techniques
• Techniques used to implement the Methodology
• Provides the descriptions of the business system
  requirements from various view points

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Tools

• Software systems
• Assists analysts and designer to build
  information systems
• Supported by Tools.
• They will not replace Systems Analysts.

E.g. Easy Case, Rational Rose, MS Visio
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Methodology
Rational Unified Process
Modeling Method or Technology
Tools
Use Case Diagrams Class Diagrams
Rational Suit Rational ROSE
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Summary

• System Life Cycles
• Why we need them
• Advantages
• Waterfall Model
• Faults with this model
• Spiral Model
• SD Life Cycle vs. SD Methodology
• System Development Methodology

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Systems Analysis and Design IT 1402