Computer Science - 1.2.3: Software Development

System Development Life Cycle

- Analysis/requirements

- Design

- Develop

- Test

- Deploy

Loops

Software development methodologies

- Waterfall

- Spiral

- Rapid Application Development

- Agile

- Extreme programming

These methods are just ways of going through the life cycle of software development.

Document Focused

documents with the requirements are constantly referred and added to.

Stages of the development are documented - proof.

Code focused

System based, looking more at code functionality, working in line with user requirements and having the users involved at all points.

What is the waterfall methodology

Linear

Document focused

development team work through each stage of the life cycle in turn until the project is completed, following the rigid structure - once a section is finished it's difficult to go back if there are any errors.

Waterfall adv

good for keeping control of a project and meeting deadlines

Workers are clear on what their roles are.

Waterfall disadv

difficult to know if the end product meets user requirements since there's no product to show until the end.

If there are problems, won't know until testing at the end of the project.

When is waterfall used

If the user requirements are clearly understood, specified and unchanging.

Suitable for simple projects - not complex.

Large projects.

Rapid Application Methodology (RAD)

working through the life cycle focusing on the front end of the software and creating a 'prototype'. Get client/consumer feedback. Implement in next prototype. Continue until client/consumer is happy with it (less time for testing).

Go and finish the back end of the software.

User requirements gathered using focus groups. Used when these requirements are unclear.

RAD Adv

good usability due to continuous feedback from client

focus groups can be used

small team

low cost

RAD Disadv

can't tell what time and budget would be

fast development so could have lots of bugs

When is RAD used

Uncertain requirements

small/medium sized project

user interaction is important

quick development

Agile methodology

A collection of methodologies which aim to improve the flexibility of software development and adapt to changes in user requirements faster.
Sprints are structured as follows: design, develop, user feedback, refine. And this repeats. Analysis is done before sprints begin.

Each sprint is an entire life cycle, each sprint adds another feature to the program.

Best for small - medium projects, but larger projects can be decomposed so work can be allocated across multiple teams and managed separately.

Agile Adv

Focuses on the product and gets versions of working software to the client to ensure that their requirements are met.

If their requirements change, it is flexible enough to adapt - due to the focus on coding (and not documentation)

have working features of code that can be tested

Agile Disadv

Can be difficult to control agile projects which could end up taking longer than originally thought. This can cause budgeting issues.

Problems can be found later on since there wasn't as much time spent on analysis

When can agile be used

where client requirements change and flexibility is required.

small-medium sized. can be for large if broken down but will take time.

Extreme programming

Type of agile that focuses on getting high quality code, almost ready to be the final product quickly.

Two programmers working on the same set of code - catch mistakes easily. Quick development and feedback. Pair programming where one person programs and the other critiques.

Extreme programming adv

error avoidance through pair programming

changes can be made at short notice

Code is clear and comprehensible at all times

Extreme programming disadv

customer must participate

relatively large time investment

higher risk - problems found later as programming is prioritised

When is extreme programming used

where speed of product delivery and high quality is necessary

mall to medium-sized teams. However, it can be adapted for use in larger projects by scaling its practices and principles to fit the needs of the larger team and project.

What is the spiral method?

The spiral model has four quadrants:

• determine objectives, where the developer determines the main objectives for the iteration and identifies any alternative solutions.

• identify and manage risk, where the developer identifies the highest risk features of the program and mitigates them by planning or creating alternative solutions

• develop and test, where the developer programs part of the project and test it

• review and plan next iteration, where developer gains client feedback and plans any modifications for the next iteration.

Client feedback then informs future development and prototypes which feedback into future revisions.

Spiral adv

Focuses on risk

ensure client is happy

better for efficient use of resources by evaluating risk early on

Spiral disadv

It can be a lengthy process due to the evaluative nature

when is spiral used

large-scale, high-risk projects. These might be projects where technologies are unproven or multiple organisations are involved.