SDLC Models

NOW,We will talk about the SDLC Models

There are 7 SDLC Models
1.Built & Fix Model
2.Waterfall Model
3.Iterative Model
4.Prototyping Model
5.Spiral Model
6.RAD Model
7.V-Model

Lets discuss each Model one by one

1.Built & Fix Model 

 This model is the worst model developing a project. In    this the product or software is built without proper specifications and design steps .In essence, the product is built and modified as many times as possible until it satisfies the client or customer.
the cost of using this model is really high 

2.Waterfall Model

   Waterfall approach was first Process Model to be introduced and followed widely in Software Engineering to ensure success of the project. In "The Waterfall" approach, the whole process of Software development is divided into separate phases.

 The phases in Waterfall model are: Requirement Specifications phase, Software Design, Implementation and Testing & Maintenance. All these phases are cascaded to each other so that second phase is started as and when defined set of goals are achieved for first phase and it is signed off, so the name "Waterfall Model". All the methods and processes undertaken in Waterfall Model are more visible. of software development is divided into separate process phases.

3.Iterative Model

In this model the project is divided into the release or increments and a end product is obtained.

In this until and unless we deliver the 1st release or increment we cannot start with the 2nd release or increment of product

4.Prototyping Model

 The prototyping model is a system development method(SDM) in which a prototype (an early approximation of a final system or product) is built ,tested and then reworked as necessary until an acceptable prototype is finally achieved from which the complete system or product can now be developed.

This model works best in scenarios where not all of the project requirements are known in detail ahead of time .It is an iterative ,trail and error process that take place b/w the developers and the users 

5.Spiral Model

Risk analysis is the main feature for Spiral Model.It is also known as spiral lifecycle model

The steps in the spiral model can be generalized as follows:

1. The new system requirements are defined in as much detail as possible. This usually involves interviewing a number of users representing all the external or internal users and other aspects of the existing system.

1. A preliminary design is created for the new system.

1. A first prototype of the new system is constructed from the preliminary design. This is usually a scaled-down system, and represents an approximation of the characteristics of the final product.

1. A second prototype is evolved by a fourfold procedure: (1) evaluating the first prototype in terms of its strengths, weaknesses, and risks; (2) defining the requirements of the second prototype; (3) planning and designing the second prototype; (4) constructing and testing the second prototype.

1. At the customer's option, the entire project can be aborted if the risk is deemed too great. Risk factors might involve development cost overruns, operating-cost miscalculation, or any other factor that could, in the customer's judgment, result in a less-than-satisfactory final product.

1. The existing prototype is evaluated in the same manner as was the previous prototype, and, if necessary, another prototype is developed from it according to the fourfold procedure outlined above.

1. The preceding steps are iterated until the customer is satisfied that the refined prototype represents the final product desired.

1. The final system is constructed, based on the refined prototype.

1. The final system is thoroughly evaluated and tested. Routine maintenance is carried out on a continuing basis to prevent large-scale failures and to minimize downtime

6.RAD

RAD stands for Rapid Application Development Model

RAD is incremental software development process model that allows usable systems to be built in as little as 60-90 days, often with some compromises. The RAD model used for information systems development. The RAD model contains the following phases:

Business modelling

Data modelling

Proccess modeling

Application generation

Testing and turnover

7.V-Model

In V-model the testing begins as soon as possible in the project life cycle.It is always good practice to involve tester at earlier phases of product life cycle. There are variety of test activities need to be carried out before end of the coding phase.This activities should be carried out in parallel to the development activities so that testers can produce a set of test deliverable.

The V-model illustrates that testing activities (Verification and Validation) can be integrated into each phase of the product life cycle

As the word comes verification and validation lets talk about them

Verification

It is the process of evaluating work products (not the actual final product) of a development phase to determine whether they meet the specified requirements for that phase or not.And to check every phase individually is called Verification of that project

Validation

It is process of evaluating the software during or at the end of the development process to determine whether it satisfies specified business requirements .It majorly focused on User's Request and User's Needs