What is Waterfall Methodology ? Advantages & Disadvantages

It's development method in which work “flows down” from one stage into the next stage. Each stage must be completed before the next stage can begin, and returning to a previous stage is often not permissible. 

The original 10 step Waterfall Methodology
The original SDLC -- the Waterfall Methodology -- is comprised of 10 steps intended to be executed sequentially, but -- depending on the size and complexity of the project -- phases can be combined or even overlap (see 6 Step Waterfall Methodology outlined below).

1.      Initiation Phase:  An opportunity is spotted, and is proposed in a formal Concept Proposal Document.

2.      System Concept Phase:

·         Deliverables: 

·         System Boundary Document (to define the scope or boundary of the concept),

·         Cost Benefit Analysis,

·         Risk Management Plan,

·         Feasibility Study. Typically evaluated in three areas:

o    economical,

o    operational,

o    technical.  

o    Note:The feasibility study is sometimes used to present the project to upper management in an attempt to gain funding.

3.      Planning Phase:

·         Used as a reference to keep the project on track and to evaluate the progress of the MIS team.

·         Deliverables:

·         A Project Management Plan is developed .

·         Note: Provides the basis of acquiring the resources needed to achieve a solution.

4.      Requirements Analysis Phase:

5.      Design Phase: The requirements are analysed in order to design the product's architecture.

6.      Development Phase:  The design is converted into reality and then white box tested by the development team.

7.      Integration and Test Phase: The product is tested by the development team,  Quality Assurance staff, and final users.

8.      Implementation/Deployment Phase: The product is rolled out into a production environment.

9.      Operation and Maintenance Phase: The system is monitored to ensure it continues to meet performance requirements, with periodic In-Process Reviews to suggest ways on improving the system.

10.  Disposition Phase: The product is removed from service, with special emphasis on archiving the data, or moving to another system.

Features of Waterfall Model

• Simple and easy flow
• Each phase lays out its deliverable, followed by a validation process
• Excellent work progress tracking system
• Best option for smaller projects where business requirements are captured in advance
• Simple and feasible
• Includes a verification process to monitor and resolve errors.

Disadvantage

The biggest drawback with this model is that once a phase is completed, there is no going back. The only option if one wants to go back to a previous phase in the life cycle is by going back to the drawing board and designing from scratch. Therefore, this makes the water fall model a good fit for smaller open source projects using Magento, Joomla, WordPress (where the requirements can be clearly defined upfront), but not for Custom Programming requirements where the business needs are constantly changing.