COSC 4P01: Week 1 Notes

Note

These notes are taken after the fact based on the slides. Anything mentioned only in lecture is not included. Covers Week 1 material (Software Processes and Process Improvement).

Software Processes

General Process Models

• Abstract representations of how software is produced
• Three main models:
  • Waterfall model
  • Incremental development
  • Reuse-oriented development

Waterfall Model

• Sequential phases: requirements → design → implementation → verification → maintenance
• Strengths: easy to manage, clear documentation
• Weaknesses: inflexible to change, late delivery of working software

flowchart TD
    R[Requirements] --> D[Design]
    D --> I[Implementation]
    I --> V[Verification]
    V --> M[Maintenance]

Incremental Development

• System delivered in small, usable increments
• Each increment builds on the last
• Benefits: early delivery, user feedback, reduced risk
• Drawback: difficult to design common facilities when requirements evolve

flowchart TD
    A[Increment 1] --> B[Increment 2] --> C[Increment 3] --> D[Final System]

Reuse-Oriented Development

• Build systems from pre-existing components
• Stages: specification → component discovery/evaluation → requirements refinement → configuration → adaptation/integration
• Requires strong component libraries

Requirements Engineering Process

• Activities:
  • Requirements elicitation
  • Requirements specification
  • Requirements validation
• Produces a requirements document that guides design & implementation

flowchart LR
    E[Elicitation] --> S[Specification] --> V[Validation]

Design Process

• Transform requirements → software architecture + detailed design
• Activities:
  • Abstract design (architecture, modules)
  • Interface specification
  • Component design

Testing

• Stages of testing:
  • Unit testing (individual components)
  • Integration testing (combined components)
  • System testing (whole system)
  • Acceptance testing (with users)
• Plan-driven processes emphasize phased, structured testing

flowchart TD
    U[Unit] --> I[Integration] --> S[System] --> A[Acceptance]

Software Evolution

• Systems must evolve to remain useful
• Evolution activities:
  • Bug fixing
  • Enhancements
  • Adaptation to new environments
• Often costs more than initial development

Software Prototyping

• Prototype: early version of system used to test ideas
• Uses:
  • Help elicit/validate requirements
  • Explore design options (esp. UI)
  • Test critical functionality
• Benefits:
  • Improved usability
  • Closer alignment with user needs
  • Better design quality
  • Reduced development effort
• Drawbacks:

  • Can mislead stakeholders if mistaken for the final system

Incremental Delivery

• Deliver system in increments, each with partial functionality
• Prioritize high-value requirements in early increments
• Advantages:
  • Early value delivery
  • Acts as prototype for feedback
  • Lower project failure risk
• Problems:
  • Hard to identify shared facilities without full specification
  • Procurement/contracts often expect complete specs up front

Process Improvement

Motivation

• Improve quality, reduce costs, speed up development
• Approaches:
  • Process maturity: better project management + engineering practices
  • Agile approach: iterative, lightweight, responsive to change

The Process Improvement Cycle

1. Measurement – collect baseline data
2. Analysis – identify weaknesses, bottlenecks
3. Change – introduce process changes
4. Repeat (continuous improvement)

flowchart TD
    M[Measurement] --> A[Analysis] --> C[Change] --> M

Process Measurement

• Collect quantitative data where possible:
  • Time (calendar time/effort)
  • Resources (person-days, hardware use)
  • Events (number of defects found)
• Use measurements to assess improvements, but organizational goals should drive changes (not metrics alone)

Capability Maturity Model (SEI)

Levels of process maturity:

Level	Description
Initial	Essentially uncontrolled
Repeatable	Basic project management defined & used
Defined	Process management strategies established
Managed	Quality management strategies established
Optimizing	Continuous process improvement strategies implemented

graph TD
    A[Initial] --> B[Repeatable] --> C[Defined] --> D[Managed] --> E[Optimizing]