Lecture 2: Overview of Systems Development Systems Development Methodologies

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Lecture 2Overview of Systems DevelopmentSystems
Development Methodologies
MIS 160 Systems Development Life Cycle I

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OVERVIEW OF SYSTEMS DEVELOPMENT

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Systems Development

• What is a system?
• A collection of related components that interact
  to perform a task in order to accomplish a goal
• Systems development (systems analysis and
• design) is the process of creating systems,
• developing them, and maintaining or enhancing
• them.

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Characteristics of Software

• Software is developed, not manufactured
• Software does not wear out
• Software is custom-built, not assembled from
  existing components

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Problems in Software Development(Software
Crisis?)

• Schedule and cost overruns
• Demand gt supply
• Poor quality
• Difficulty in maintenance
• Don't support business objectives
• Failure to satisfy user requirements
• Computers and software that no one needs
• Incompatible and inadequate technology
• Poor cost/benefit analysis

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Success/Failure of IS Projects

• Average costs of systems development projects
  for
• large companies 2,322,000
• medium companies 1,331,000
• small companies 434,000
• Average failure rate of projects for
• large companies 72 percent
• medium companies 84 percent
• small companies 91 percent

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Alleviating the Problems in Systems Development

• Elimination of the causes of system failure lie
  in
• 1. the application of methodologies
• 2. modeling tools
• 3. techniques
• 4. project management techniques
• to design and build IS that not only meet the
  needs of the
• users, but also are delivered on time and within
  budget

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Principles of Successful Systems Development

• Get the user involved
• Use a problem-solving approach
• Establish phases and activities
• Establish standards for development and
  documentation
• Justify systems as capital investments
• Don't be afraid to cancel or revise scope
• Divide and conquer
• Design systems for growth and change
• Proper planning and project management

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Some Key Terms ...

• Systems development life cycle (SDLC) the life
  of a project, from concept through implementation
• Methodology a comprehensive and detailed
  version of an entire SDLC
• Technique an approach that applies specific
  tools and rules to complete one or more phases of
  the methodology
• Modeling tools specific tools used to apply
  techniques
• Project management techniques tools used to
  help plan, schedule, and control a project

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BEWARE

• Writing code without a well-thought-out system
  request rarely works.

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SDLC

• The step by step process followed during systems
  analysis and design
• Steps
• Project Planning
• Requirements Analysis
• System Design
• Build the System/Resource Acquisition
• Implementation and Maintenance

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The SDLC

• 1. Planning
• a. Project identification and selection
• b. Project initiation and planning
• 2. Analysis
• a. Determine system requirements (WHAT users
  need)
• b. Modeling possible solutions (HOW to satisfy
  user needs)
• 3. Design
• a. logical design
• b. physical design
• 4. Implementation
• 5. Maintenance / support

Frontend
A
D
Backend
I
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Project Planning

• Preliminary Analysis
• Determine the organization objectives
• Internal and external documentation
• Interviews
• Determine the nature and scope of the problem
• Look at alternative solutions
• Describe Costs and Benefits
• Document!!

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Requirements Analysis

• Gather data
• documents
• interviews
• questionnaires
• Analyze the data
• CASE tools
• Document!!

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System Design

• Preliminary design
• General functional capabilities of the system
• Prototyping
• Detailed design
• How the system will deliver on the preliminary
  design
• Document!!

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Build the System/Resource Acquisition

• Obtain the hardware and software
• Test the system

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Implement Maintain

• Converting to new system
• Direct
• Parallel
• Phased
• Pilot
• Training the users
• Audit and Evaluate

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Processes and Deliverables
Process
Product
Project Plan System Proposal System
Specification New System and Maintenance Plan
Planning Analysis Design Implementation
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Breakdown of Effort

• Actual
• Analysis 20
• Design 20
• Implementation 60
• Coding 20
• Testing and
• Debugging 40

Should be Analysis 40 Design 40 Implementati
on 30
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SYSTEMS DEVELOPMENT METHODOLOGIES

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Some Common Development Methodologies and
Techniques

• Code fix model
• Structured development
• Spiral model
• Prototyping
• Rapid application development
• Object-oriented development

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Code and Fix It Model

• An early technique
• The developer, in the following order
• codes
• thinks about requirements
• fixes the code
• continues this process until...

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Structured Development(Waterfall Model)
Project Identification and Selection
Project Initiation and Planning
Analysis
Logical Design
Physical Design
Implementation
Maintenance
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Advantages of Structured Development

• Been used successfully for over 20 years
• Provides a clear framework that defines and
  divides important activities
• Can be applied to both small and large projects
• Division of labor is easier to facilitate

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Limitations of Structured Development

• Specification problems
• assumes that development is a sequential process
• Changing requirements
• requirements specified at the beginning
• assumption that requirements will not change
• Conceptualization and visualization
• document led methodology
• volume of documentation can be huge
• Inaccuracy
• there is only downward trend

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The Spiral Model

• Boehm, 1988
• Risk-driven, rather than code-driven
• Uses process modeling rather than methodology
  phases

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The Spiral Model

• Development process
• product separated into critical parts/levels
• risk analysis at each level (risk reduction)
• prototyping at each level
• same steps at each level
• Enhancement process
• same as the development process

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The Spiral Model

• Requires
• competent systems management
• competent systems personnel
• involved users

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The Spiral Model
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Prototyping

• Principle a user can tell you better what they
  DON'T want than what they DO want
• Expendable (throw-away) prototyping
• discarded after use
• used to support the analysis and design phases
• Evolutionary prototyping
• prototype evolves into the final system
• is it a methodology?

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Advantages

• Speed
• Easier for end-users to learn
• System changes discovered earlier
• End-user involvement (ownership)
• increased user satisfaction
• increased user acceptance
• User-analyst communication
• Early problem detection
• reduced development time
• reduced maintenance

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Disadvantages

• Poor documentation
• Hard to control/manage
• (Unrealistic) User expectations
• time for final system
• final system differences
• reduced analysis

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Rapid Application Development(RAD)

• Logistical approach to systems design
• Combines
• integrated CASE tools
• information engineering methodologies
• management techniques
• Speeds up Systems Development by as much as 20
  times
• Critics consider it incomplete life cycle

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Object-Oriented (OO) Development

• A fundamentally new way of thinking about
  developing systems
• Object-oriented means that we organize software
  as a collection of discrete objects that
  incorporate both data and behavior
• Object-oriented development an approach to
  systems development that proposes the use of
  objects in the building of new systems and the
  rebuilding of old ones

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Advantages of OO

• Faster development
• Higher quality
• Easier maintenance
• Increased scalability
• Better information structure
• Increased adaptability
• Increased modeling power
• Supports complexity

Reuse
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Disadvantages of OO

• Maturity of technology
• Need for standards
• Lack of database technology
• Lack of reusable software
• Lack of metrics
• Speed of execution
• Availability of qualified personnel
• Cost of conversion