OCR A-level Computer Science — 1.2.3 Software Development

Describe the purpose of Software Development Methodologies. [2]

• structured framework/lifecycle of clear stages

• allows project managers to monitor and review progress towards the completion of software

Name three of the main stages of a Software Development Methodology. [3]

• analysis

• design

• development

• testing

• evaluation

(max 3)

Describe the Waterfall Lifecycle. [4]

• stages are linear // stages are completed sequentially

• each stage must be finished before the next can begin

• the client is (generally) only involved at the start and end // establishes requirements in early stages

• does not allow backtracking to previous stages // all intervening stages must be revisited if necessary to return to a previous stage

• the project is reviewed at the end of each stage

• formal documentation is produced at each stage

(max 4)

Describe a type of project for which using the Waterfall Lifecycle would be appropriate. [1]

Projects with very clear/unchanging deliverables // Small projects // Simple projects

Compare the benefits and drawbacks of using the Waterfall Lifecycle. [4]

Benefits:

• simple to follow and manage

• each stage has clear deliverables

Drawbacks:

• very inflexible

• high risk factor

• unsuitable for projects with variable requirements // unsuitable if end user requires lots of involvement

(max 2 benefits, 2 drawbacks; 4 total)

Describe the Spiral Model. [4]

• iterative approach // focus on generating prototypes

• features are added incrementally

• the four quadrants (determine objectives, identify and manage risk, devlop and test, plan next iteration) manage risk

• large emphasis on minimising risk

• heavy focus on documentation

• frequent client feedback informs future development

(max 4)

State the four quadrants of the Spiral Model. [4]

ORDI

• determine objectives

• identify and manage risk

• develop and test

• plan next iteration

(max 4)

Describe a type of project for which using the Spiral Model would be appropriate. [1]

Projects with variable deliverables // Large projects // Complex projects

Compare the benefits and drawbacks of using the Spiral Model. [4]

Benefits:

• focus on risk reduces the chance of the project failing

• functionality can be added after initial analysis

• protoypes produced early so user can give feeback (to be acted upon)

Drawbacks:

• high cost

• risk analysis is a specialised skill

• more complex means time management is more difficult

(max 2 benefits, 2 drawbacks; 4 total)

Explain what is meant by Extreme Programming (XP). [4]

• (XP is a) software development methodology

• (extreme) iterative approach // program is regularly reviewed

• focus on good-quality code

• (XP is an) agile paradigm

• designed to allow development to respond to changing user requirements

• involves paired programming

(max 4)

Describe a type of project for which using Extreme Programming (XP) would be appropriate. [1]

Projects with variable deliverables // Projects whose code needs to be efficient // Projects where risk of bugs is very high

Compare the benefits and drawbacks of using Extreme Programming (XP). [4]

Benefits:

• quiality of end code very high

• efficient code // few bugs

• easily adapts to changing user requirements

Drawbacks:

• high (short-term devlopment) cost

• regular client contact needed

• slower than more aggressive iterative approaches

(max 2 benefits, 2 drawbacks; 4 total)

Explain what is meant by Agile Methodologies. [2]

• a collection of methodologies

• (follow an) agressive iterative approach

• incremental prototypes (are built)

• focuses on delivery to customers // frequent customer interaction

(max 2)

Give two examples of Software Development Methodologies that would be described as Agile Methodologies. [2]

• Rapid Application Devlopment (RAD)

• Extreme Programming (XP)

Describe the Rapid Application Development (RAD) process. [4]

• prototype is created

• (evaluated and) feedback used to inform next iteration

• any changes are made

• process repeated until …

• … prototype becomes final product

(max 4)

Describe a type of project for which using the Rapid Application Development (RAD) process would be appropriate. [1]

Projects with variable deliverables // Projects whose code needs to be high-quality

Compare the benefits and drawbacks of using the Rapid Application Development process. [4]

Benefits:

• user involved throughout development process

• end product more likely to match user requirements

• easily adapts to changing user requirements

Drawbacks:

• quiality of end code not very high

• regular client contact needed

• doesn’t scale well to large projects

(max 2 benefits, 2 drawbacks; 4 total)