The waterfall model is generally attributed to Royce (1970). The model encourages the product development team to specify what the software is supposed to do (gather & define requirements) before implementing the system. Product development is split into multiple sequential steps (design, implement, test) with intermediate deliverables leading to a final product.
To ensure proper execution with good quality, each step has defined entry and exit criteria. The ETVX (Entry-Task-Validation-eXit) model proposed by IBM fits the waterfall approach wherein each phase may be considered as an activity structured using the model.
The waterfall model may be viewed as a divide-and-conquer approach to development. It allows for tracking project progress across phases and forces the organization to adopt a more structural approach to developing software. The model also requires documentation to be generated which will be used to test and maintain the system. The waterfall model emphasizes careful analysis before building the system. The idea is to avoid wasted effort in building something which does not meet the customer's requirements. Hence, attempt is made to fully specify and finalize customer requirements as early as possible. Requirements are documented in the requirements specification document. In subsequent phases, “verification” activities are performed to ensure conformance to requirements listed in the requirements specification document. A problem with this sort of reliance on the requirements document is the possibility of incomplete or incorrect requirements being specified. Adequate “validation” with the customer is required.
At a high level, the waterfall model comprises the following phases.
To ensure proper execution with good quality, each step has defined entry and exit criteria. The ETVX (Entry-Task-Validation-eXit) model proposed by IBM fits the waterfall approach wherein each phase may be considered as an activity structured using the model.
The waterfall model may be viewed as a divide-and-conquer approach to development. It allows for tracking project progress across phases and forces the organization to adopt a more structural approach to developing software. The model also requires documentation to be generated which will be used to test and maintain the system. The waterfall model emphasizes careful analysis before building the system. The idea is to avoid wasted effort in building something which does not meet the customer's requirements. Hence, attempt is made to fully specify and finalize customer requirements as early as possible. Requirements are documented in the requirements specification document. In subsequent phases, “verification” activities are performed to ensure conformance to requirements listed in the requirements specification document. A problem with this sort of reliance on the requirements document is the possibility of incomplete or incorrect requirements being specified. Adequate “validation” with the customer is required.
At a high level, the waterfall model comprises the following phases.
- Requirements
- Design
- Development / Implementation
- Testing
- Maintenance
In the next blog post, we shall briefly look at some of the advantages and disadvantages of this model.
