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 - ff 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?

• Suits large scale projects

• Suits projects with stable requirements

• Suits low risk projects

What are the benefits of the waterfall lifecycle?

• Straightforward to manage

• Clearly documented

What are the drawbacks of the waterfall lifecycle?

• Lack of flexibility

• 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

• Less focus given to documentation and more to user satisfaction

What types of project are agile methodologies suited to?

• Projects with unclear initial requirements.

• Small to medium scale projects

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?

• High cost of two people working on one project

• 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

• Used when the program is complete

• 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 source code to checks 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