Software developement

Made with help from PMT Comp. Sci. notes

The 5 developement methodologies you need to know

• Waterfall lifecycle

• Agile methodologies

• Extreme programming

• Spiral model

• Rapid application development

Waterfall lifecycle

• Includes analysis, design, implementation, evaluation and maintanance stages

• The stages are completed in sequence

• Phases can be revisited back in turn

• Inflexible - if a change occurs in the requirements the lifecycle cannot respond easily, often at the cost of time and money.

What types of project are the waterfall lifecycle suited to?

Suited to large scale, low risk projects with stable requirements

What are the benefits of the waterfall lifecycle?

• Straightforward to manage

• Clearly documented

What are the drawbacks of the waterfall lifecycle?

• Can’t easily adapt to changing user rquirements

• No risk analysis

• Limited user involvement

Agile methodologies

• A collection of methodologies which aim to improve the flexibility of software development and adapt to changes in user requirements faster

• A working prototype is delivered early on and is built upon in an iterative manner so that new prototypes are delivered regularly throughout the developement process

• Less focus is given to documentation and more to user satisfaction

What types of project are agile methodologies suited to?

Projects with unclear initial user requirements.

What are the benefits of agile methodologies?

• Produces high quality code

• Flexible to changing requirements

• Regular user input

What are the drawbacks of agile methodologies?

• Poor documentation

• Requires consistent interaction between user and programmer

Extreme programming (XE)

• Programming stage is main focus

• Is a form of agile developement

• Includes planning, design, code, test stages

• Testing is focused throughout developement

• Prioritises code quality over documentation

• Encourages the use of pair programming

What types of project are extreme programming suited to?

• Projects with unclear initial requirements.

• Projects requiring excellent usability

• Small to medium scale projects

What are the benefits of extreme programming?

• Produces high quality code

• Constant user involvement means high usability

What are the drawbacks of extreme programming?

• Peer programming can increase cost

• Teamwork is essential

• End-user may not be able to be present

Spiral model

• Incremental design

• Includes planning, design, programming and evaluation stages

• At the end of all 4 phases it repeats

• Each cycle usually adds a new element to the problem

• Is used to manage risk

• Prioritises riskiest elements first

What types of project are suited to the spiral model?

• High risk projects

• Suited to very large scale projects

• High budget projects because risk management involves hiring risk assessors which is expensive

What are the benefits of the spiral model?

• Thorough risk-analysis and mitigation

• Caters to changing user needs

• Produces prototypes throughout

What are the drawbacks of the spiral model?

• Expensive to hire risk assessors

• Lack of focus on code efficiency

• High costs due to constant prototyping

Rapid application developement (RAD)

Iterative methodology:

• Innitial user requirements are used to create a prototype.

• This is given to users for evaluation and feedback

• Feedback is used to inform any changes made in the next iteration of the prototype

• This process repeats until requirements of end-users are met at which point the prototype becomes the final product

What types of project are suited to rapid application developement?

• Small to medium projects

• Low-budget projects

• Projects with short time-frames.

What are the benefits of rapid application developement?

• Caters to changing user requirements

• Highly usable finished product

• Focus on core features, reducing development time

What are the drawbacks of rapid application developement?

• Poorer quality documentation

• Fast pace may reduce code quality

Alpha testing

• Testing by the developers

• Testing in the way the end user would

• Takes place before beta testing

Beta testing

• Takes place after alpha testing

• Testing by end users

• Feedback from users is used to inform the next stage of development

Describe white box testing

• Using the source code to create a set of tests that check every possible path through the program

• Uses dry runs and/or trace tables

Describe black box testing

• Tests the expected output based on input

• Does not look at the code / looks only at program specification

• Can be carried out by developers or end users

Advantages of a modular approach

• Work is easier to divide between a team - each team member just needs to know what values go into their subroutine and the expected functionality

• Saves time as work takes place in parallel

• Each team member can work on their area of expertise.

• Breaks problems into smaller area

• Easier to test/ debug/ read

• Each subroutine can be tested before integration.

• Code can be reused in the project/ future projects