Chapter 1 - Systems Development Methodologies

define:

• computer science
• computer information systems

A) People and Systems Design

• systems analysts - build ISs
• end-user involvement

B) The Challenge to Develop Better Information Systems

The Software Crisis

symptoms -

1. late completion,
2. cost overruns,
3. not reliable,
4. user-friendly, etc.

1979 study by U.S. Comptroller General: all government-contracted software

• only 2% delivered products that worked on delivery
• 3% worked after some minor corrections
• 45% delivered but never successfully used
• 20% used after extensive reworking
• 30% never delivered

Factors contributing to the software crisis:

• 1. Dramatic advances in hardware and operating systems
• 2. Dramatic decreases in hardware costs
• 3. Increasing demand for new software systems, with a resulting application backlog
• 4. Haphazard approaches to software development

What makes a system Unsuccessful?

1. did not support business strategies & objectives
2. poor systems planning & inadequate project management
3. failure to define/understand user requirements
4. negligence in estimating costs/benefits
5. creation of a myriad of design defects/errors
6. computers/software that no one needs or knows how to use
7. incompatible / inadequate technology
8. negligence in implementing adequate controls
9. unstructured /unmaintainable software
10. inadequate implementation tasks

What makes a system successful?

1. stressing user involvement
2. implementing systems planning
3. using project management techniques
4. developing alternative systems design for evaluation before making major commitments
5. designing all components functionally
6. using detailed functional design as a guide
7. preparing clear, complete, and current documentation
8. using coordinated, planned approach to systems implementation
9. performing postimplementation reviews
10. designing for and performing systems maintenance

SOFTWARE MODELS

• software lifecycle
• prototyping

C) Systems Development Life Cycle (SDLC) - (Fig. 1.1)

• Front-end Phases of Systems Development (Fig. 1.2)
• Systems Planning Phase

Feasibility Factors (TELOS)

• Technical Feasability
• Economic Feasability
• Legal Feasability
• Operational Feasability
• Schedule Feasability

Strategic Factors (PDM)

• Productivity
• Differentiation
• Management

Back-end Phases of Systems Development (Fig. 1.3)

• requires a Systems Design Walkthrough
• implementation plan usually in the form of GANTT & PERT charts
• implementation tasks:
• software development
• site preperation
• equipment installation
• testing
• training
• documentation preperation
• conversion
• postimplementation review

software development life cycle

1. software designing
2. software coding
3. software testing
4. documentation
   • systems documentation
   • software documentation
   • operations documentation
   • user documentation
5. implementation
   • direct
   • parallel
   • phase-in
   • pilot

D) Maintaining the System after it is Implemented

longest and costliest phase of the systems life cycle

E) Using Prototyping to Design a Working System Model

• designed to allow sponsors and users to "play" with a scaled-down version, or prototype, of a working system before final specification is agreed upon. (Fig. 1.4)
• how prototyping fits into the SDLC (Fig. 1.5)
• when to use prototyping (Fig 1.6)

F) The Information Engineering Methodology

Information Engineering Life Cycle (IELC)

• information strategy planning
• business analysis
• business systems design
• technical design
• construction
• transition
• production

Information Engineering Methodology (IEM)

• systems planning
• systems analysis
• systems design
• systems construction and implementation

Ideal Systems Development Methodology

• interact with and encourage user involvement
• reduce time and cost of development
• provide rigor and discipline to the development process
• improve systems quality
• produce complete & accurate design specs and documentation
• produce a systems that meets user requirements and is easy to maintain

G) Joint Application Development: A Technique for involving Users in Systems Development (Fig. 1.8)

Exercises: look over 1-18, 23; turn in 19-22