Ability to develop systems	Waterfall	Parallel	Iterative	System Prototyping	Throwaway Prototyping	Spiral
With unclear user requirements	Poor	Poor	Good	Excellent	Excellent	Excellent
With unfamiliar technology	Poor	Poor	Good	Poor	Excellent	Excellent
That are complex	Good	Good	Good	Poor	Excellent	Excellent
That are reliable	Good	Good	Good	Poor	Excellent	Excellent
With a short time schedule	Poor	Good	Excellent	Excellent	Good	Poor
With schedule visibility	Poor	Poor	Excellent	Excellent	Good	Poor

1. Software Development Methodology

Methodology: A formalized approach to implementing the SDLC

-> A series of steps to perform and deliverables to produce

Methodology Sources

1.Internally developed by organizations
2.Consulting firms
3.Software vendors
4.Government agencies

2. Structured Systems Development

Based upon SDLC
Assumes a project phase is complete before moving to the next phase

1. Waterfall Development

2. Parallel Development

3.V-model

Goal – doing each phase thoroughly before moving forward ensures correct and high-quality outcomes

2.1. Waterfall Development Methodology

Move from phase to phase
Emphasis on deliverables from one phase flowing into the next phase
Originates in the manufacturing and construction industries
Is a systematic and sequential approach towards software development.
Follows the phases of SDLC in a Sequence.
Each phase begins or originates only after the previous phase has finished.
Highly structured physical environments in which after-the-fact changes are prohibitively costly, if not impossible.

2.1.1. Advantages

System requirements identified long before construction begins
Requirements are “frozen” as project proceeds – no moving targets allowed

2.1.2. Disadvantages

Must wait a long time before there is “visible” evidence of the new system
Takes a long time from start to finish

2.2. Parallel Development Methodology

Subdivide the project into subprojects that can be worked on at the same time.
Reduce the overall project length

2.2.1. Advantages

Reduces overall project time (compared to Waterfall)
Reduces the need for rework; with shorter time frame, less chance of requirements changing

2.2.2. Disadvantages

Creating sub projects requires careful design decisions
Integrating subprojects at the end can be complex and difficult

3. Rapid Application Development

Incorporate special techniques and tools:

1) JAD sessions

2) Visual programming languages

3) Code generators

Goal – get some portion of system developed quickly and in the users’ hands
Three RAD Approaches

1. Iterative development

2. System Prototyping

3. Throw-away prototyping

3.1. Iterative Development Methodology

A series of versions developed sequentially

3.1.1. Advantage

Users get a system to use quickly
Users identify additional needs for later versions based on real experiences with current version

3.1.2. Disadvantage

Users faced with using an incomplete system for a time
Users must be patient and wait for fully-functional system

3.2. System Prototyping Development Methodology

Create prototype (model) of system and “grow” it into the final system

3.2.1. Advantages

Users get to work with prototype very quickly
Feedback cycles let users identify changes and refine real requirements

3.2.2. Disadvantages

Superficial analysis may cause problems
Initial design decisions may be poor
Overlooked features may be hard to add later

3.3. Throwaway Prototyping Development Methodology

Adds emphasis on experimenting with design options before design is finalized
Design options are thrown-away, but learning from them is factored into final design

3.3.1. Advantages

Uncertainty is minimized
Important issues are understood before building the final system

3.3.2. Disadvantages

May take longer (compared to system prototyping)

4. Spiral development methodology

Is a model introduced by Barry Boehm in 1986.
Combines iterative and prototype development with the systematic, controlled aspects of the waterfall model.
A very high emphasis on risk analysis

4.1. Quadrant 1: Planning

Determine objectives, alternatives, and constraints.

4.2. Quadrant 2: Risk Analysis

Evaluate alternatives, identify, resolve risks.

4.3. Quadrant 3: Development & Test

Develop, verify, next-level product.

4.4. Quadrant 4: Evaluation

Analyze feedback and plan next phases.

4.5. Advantages

Focus on risk analysis.
Good for large and mission critical projects
A working software is produced early
The design does not have to be perfect
Early and frequent feedback from users
Cumulative costs assessed frequently

4.6. Disadvantages

Can be a costly model to use.
Risk analysis requires expertise.
Success is highly dependent on the risk analysis phase.
Doesn’t work well for smaller projects.

4.7. When spiral is good to use

For medium to high-risk projects
New technology to be used
Complex, constantly changing and continuous Requirements
Significant changes are expected (research and exploration)
Users are unsure of their need

5. Summary

There are many different Software Development Methodologies
It is important to select the methodology before starting the project
Select the best methodology based on the project characteristics

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SOFTWARE DEVELOPMENT METHODOLOGIES – TRADITIONAL METHODOLOGIES