Unit 12 - Program development life cycle

Purpose of PLDC

• Easier to manage

• Easier to plan/cost

• Clear deliverables produced at the end of stage

“Three activities that take place during development stage”

• Data structures

• Algorithms/flowcharts/pseudocode

• Modules (program structures)/ module - team allocation

• Testing method/plan

• Choice of programming language

Documents produced in analysis stage

• Problem definition

• Requirements specification

• Documents related to current system (Feasibility study)

Meaning of downward arrows in PLDC diagram

• Result from one stage is passed to the next

Meaning of upward arrows in PLDC diagram

• More work is required at a previous stage to complete the current stage

Analysis

• The problem is identified

• The developer discusses the program requirements with the customer

• A ‘requirements specification’ document is produced that details what is required from the program

Design

• An identifier table is produced

• Data structures

• What algorithms, flowcharts and pseudocode will be used

• What modules will be used and which member of the team will be allocated to what

• What programming language will be used 

Coding

• All design stages (such as algorithms, flowcharts and pseudocode) are converted into chosen program code

• Modules assigned to each team member based on level of experience

• Syntax errors can occur, are addressed and solved

Testing

Test table is produced

• Carried out by a small group of potential costumers

• Users help to identify any errors or bugs in the software

• They can then help to feedback suggestions that can help improve the software

• Any problems are then fixed before final release 

Principles of waterfall model

• Lifecycle is carried out sequentially, in order

• Each stage must be completed before going on to the next

• Takes longer than other models because each stage must be complete before going to the next stage

• Full documentations + lots of planning

Waterfall model

Produced on at end of process

(Must finish all stages before there is a final product)

Drawbacks of waterfall model

• Concentrated, problems often found late into testing phase

• Difficult and costly to change requirements later

• No working program until late in life cycle - slower to market than competitors

• High amount of client feedback needed

Iterative development

Main focus is continuous development

Principles of iterative development

• Cycles of design, implement, test, review run repeatedly

• Produced early and frequently

• High tolerance, easily incorporated into the next cycle

• Distributed and mitigated early

Benefits of iterative development

• Allows release of working parts sooner (match market demand quickly)

• Reduced risk (find issues early)

• Easier to test and debug

• Improved quality (continuous testing and feedback)

• Higher flexibility/adaptation

Drawbacks of iterative development

• Complex to manage

• Architecture issues from revolving requirements

• Difficult to fix hard deadlines/costs

• Heavy reliance on constant involvement of customer

• Endless refinement (needs of client may keep changing)

Rapid application development

(Not a finished product, work on small sections of the code at the same time)

• Designed to get a version out as quickly as possible

Principles of RAD development

• Modules are developed in parallel

• Minimal planning is carried out/allows for changes to requirements

• Flexible development process

• Small incremental releases are made, each adding functionality

• Used for time critical development

• Client involved during all stages of development

“Benefits of RAD”

• Quicker development possible/multiple areas can be worked on at the same time

• Prototype produced at early stage in process

• Easier to change requirements

• Early review possible

“Drawbacks of RAD”

• Difficult to estimate cost/time to complete project

• Documentation often omitted

• Lack of client availability throughout cycle (too easy for client to keep changing their mind)

“Identify and describe a final stage of testing”

• Beta testing

• Testing carried out by a small group of potential users

• Users will check that the website/software works as required

• Users will feedback problems/suggestions for improvement

• Problems/suggestions identified are addressed

“Reasons why waterfall model wouldn’t be suitable for program development”

• No working software until late in the life cycle so slower to market than competitors

• More difficult to cope with changes to the requirements

• Needs high involvement/feedback of the customer

“Reasons to use Iterative/RAD model”

• Provides a working model/prototype at an early stage for client review/approval

Benefits of waterfall model

• Easy to manage, stages are completed one at a time and do not overlap

• Each stage has clear/specific deliverables (detailed documentation)

• Leaves little room for clients to change mind (project planned out) = smoother development