The Waterfall Model is the earliest method of structured system development. Although it has come under attack in recent years for being too rigid and unrealistic when it comes to quickly meeting customer’s needs, the Waterfall Model is still widely used. It is attributed with providing the theoretical basis for other SDLC models because it most closely resembles a “generic” model for software development
The Waterfall Model consists of the following steps:
1) System Conceptualization – Refers to the consideration of all aspects of the targeted business function or process, with the goals of determining how each of those aspects relates with one another, and which aspects will be incorporated into the system.
2) Systems Analysis – Refers to the gathering of system requirements, with the goal of determining how these requirements will be accommodated in the system. Extensive communication between the customer and the developer is essential.
3) System Design – Once the requirements have been collected and analyzed, it is necessary to identify in detail how the system will be constructed to perform necessary tasks. More specifically, the System Design phase is focused on the data requirements (what information will be processed in the system?), the software construction (how will the application be constructed?), and the interface construction (what will the system look like? What standards will be followed?).
4) Coding – Also known as programming, this step involves the creation of the system software. Requirements and systems specifications from the System Design step are translated into machine readable computer code.
5) Testing – As the software is created and added to the developing system, testing is performed to ensure that it is working correctly and efficiently. Testing is generally focused on two areas: internal efficiency and external effectiveness. The goal of external effectiveness testing is to verify that the software is functioning according to system design, and that it is performing all necessary functions or sub-functions. The goal of internal testing is to make sure that the computer code is efficient, standardized, and well documented. Testing can be a labor-intensive process, due to its iterative nature.
There are a variety of potential deliverables from each life cycle phase. The primary deliverables for each Waterfall phase are shown in Table along with “What is tested” and “Who performs the testing.”
| Development Phase | Deliverable | What is Tested | Who Perform Testing |
| System Conceptualization | Statement of need | Feasibility of System | Business Analysts, Product Owner, Testers |
| Systems Analysis | Statement of user requirements | Completeness and accuracy of requirements in describing user need | Business Analysts, Product Owner, Testers |
| System Design | System design specification | Completeness and accuracy of translation of requirements into design | Design Analysts, DBA, Developers, Testers |
| Coding | Application software | Design specifications translated into code at module level | Developers |
| Dynamic Testing | Tested system, error reports, final test report | Requirements, design specifications, applications software | Developers, Testers, Users |
| Maintenance | System changes | Requirements, design specifications, application software | Developers, Testers, Users |
Problems/Challenges associated with the Waterfall Model
Although the Waterfall Model has been used extensively over the years in the production of many quality systems, it is not without its problems. Criticisms fall into the following categories:
– Real projects rarely follow the sequential flow that the model proposes.
– At the beginning of most projects there is often a great deal of uncertainty about requirements and goals, and it is therefore difficult for customers to identify these criteria on a detailed level. The model does not accommodate this natural uncertainty very well.
Developing a system using the Waterfall Model can be a long, painstaking process that does not yield a working version of the system until late in the process.