Software Development Models

Nguyen Trung Lap

Hoa Sen University

Contents

Software development process

Waterfall model and V model

Iterative and incremental model

Agile model

Conclusion

Software development process

A structure imposed on the development of a software

There are several models for such processes

• Waterfall

• Spiral

• Iterative and incremental

• Agile

Each model contains a variety of tasks or activities that

take place during the process

SDLC

Video SDLC

Waterfall Model

A sequential software development process

Progress is seen as flowing steadily downwards (like a

waterfall)

Phases: Requirement, Design, Implement, Testing and

Maintenance

Serves as a baseline for many other lifecycle models

Unmodified waterfall model

Modified waterfall model

Waterfall Model

Disadvantages:– Difficulty of change after the process is underway– One phase has to be complete before moving onto the next one– Inflexible

Good for:– Requirements are well-understood– Changes will be fairly limited during the design process– Few business systems have stable requirements– Large projects where a system is developed at several sites

V model

The extension of the waterfall model

The process steps are bent upwards after the coding

phase, to form the typical V shape.

V-Model show the relationships between development

phases and its associated phase of testing

V model

Integration andComponent

Test Planning

Unit TestPlanning

SystemTest Planning

AcceptanceTest Planning

AcceptanceTest Execution

SystemTest Execution

Integration andComponent

Test Execution

Unit TestExecution

SystemObjectives

Requirements

Design

Coding

Fault Detection& Removal

Verification stages

Validation stages

V model strength

Emphasize planning for verification and validation of

the product in early stages of product development

Each deliverable must be testable

Project management can track progress by milestones

Easy to use

V model weakness

Does not easily handle concurrent events

Does not handle iterations or phases

Does not easily handle dynamic changes in

requirements

Does not contain risk analysis activities

When to use V model

Excellent choice for systems requiring high reliability

All requirements are known up-front

When it can be modified to handle changing

requirements beyond analysis phase

Solution and technology are known

Iterative and incremental model

A cyclic software development process

Developed in response to the weaknesses of the

waterfall model.

It starts with an initial planning and ends with deployment

with the cyclic interactions.

Parts of the RUP, Extreme, Agile programming

Iterative and incremental model

Iterative and incremental model

Develop a system through repeated cycles (iterative)

and in smaller portions at a time (incremental)

Take advantage of what was learned during the

development of earlier portions or versions

Start with subset of the software requirements and

iteratively enhance until the full system is implemented.

At each iteration, new functional capabilities are added.

Iterative model’s phases

Inception identifies project scope, risks, and requirements

Elaboration delivers a working architecture that mitigates

the top risks and fulfills the non-functional requirements.

Construction incrementally fills-in functional requirements.

Transition delivers the system

Each of the phases may be divided into 1 or more

iterations

Iterative model strength

Develop high-risk or major functions first

Each release delivers an operational product

Customer can respond to each build

Uses “divide and conquer” breakdown of tasks

Lowers initial delivery cost

Initial product delivery is faster

Customers get important functionality early

Risk of changing requirements is reduced

Iterative model weakness

Requires good planning and design

Requires early definition of a complete and fully

functional system to allow for the definition of increments

Well-defined module interfaces are required (some will

be developed long before others)

Total cost of the complete system is not lower

When to use iterative model

Risk, funding, schedule, program complexity, or need for

early realization of benefits.

Most of the requirements are known up-front but are

expected to evolve over time

A need to get basic functionality to the market early

On projects which have lengthy development schedules

On a project with new technology

Agile development

A group of software development methodologies based

on iterative development

Requirements and solutions evolve through collaboration

between self-organizing, cross-functional teams

Encourages frequent inspection and adaptation,

teamwork, self-organization and accountability

Agile model

Agile model characteristic

Iterations are short time frames (time boxes) 7-30 days.

Cross-functional and self-organizing without

consideration for roles of team members

Emphasize face-to-face communication

Team size is typically small (5-9 people)

Summary

Software development is the development of a software

product in a planned and structured process

There are several models for such processes

• Waterfall

• V model

• Iterative and incremental

• Agile

Waterfall vs Agile model video

Thanks for your listening!

Questions