Two types: Plan-driven and Agile.
All processes involve:

• Software specification - What the software should do
• Design and implementation - How it should be organised and implemented
• Validation - Checking it does what the customer asked
• Evolution - Changing the software over time

Software specification

• Define which services are required and limitations of the system
• Idea: Create a document that anyone could use to build the system

Stages of requirements engineering:

• Feasibility study - Produce feasibility report
• Requirements, elicitation and analysis - Looking at existing documentation, talking to customers, discussion of features, etc.
• Requirements specification - Formal list of realistic requirements
• Requirements validation - Give the specification to the customer

Plan driven methodologies

• All process activities planned in advance
• Progress measured against plan
• Do not deviate from plan

Waterfall Model

• Strict linear ordering of processes - one must be complete before the next begins
• Failure on any step means restarting

Incremental Development

• In stages, customer feedback between iterations
• Specification, development and validation can take place concurrently
• Each step is still planned in full, and tested against it’s specification

Reuse-oriented

• Uses common off-the-shelf systems (COTS), or large company libraries
• Typically good for webapps, frameworks etc.
• Development can be rapid and less costly
• Less testing needed on pre-implemented features

Agile methodologies

• Specification, design and implementation interleaved
• Stakeholders give feedback at every stage
• Manifesto: Customer involvement, Incremental delivery, People not process, Embracing change, Maintain simplicity
• Less focus on documentation, needs heavy customer involvement and small, experienced teams
• Can produce prototypes & Minimum Viable Products

All agile methodologies share these disadvantages.

Extreme Programming (XP)

• Everything super fast: Incrementl delivery, fast iterations, automated builds and tests, continual code refactoring
• Customer builds every ~2 weeks
• Implement smallest possible change to create feature for atomic functionality
• Design for feature done just before implementing that feature
• Test-driven development: Write test before implementing
• Collective ownership: ≥2 people responsible for any section of code

Scrum

• 3 stages: Outline planning, Sprint cycles, Project closure
• Sprints: ~2-4 weeks, daily meetings, items completed from backlog
• Scrum master: interfaces between dev team and customer
• Good if you want to manage a project in chunks, have unstable requirements and want smaller release cycles

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