Waterfall vs. Agile Methodology
Most software development projects apply either the Waterfall or Agile methodology. A development methodology is the procidure used by an engineering team in order to create a desired product. The Waterfall methodology represents the traditional approach, where the development process is conducted in a linear series of events. On its way toward the conclusion the progress flows continously through the phases of a project (analysis, design, development, testing, release) like a waterfall. The entire project is planned in advance. Agile is a more recently developed software development methodology, where the linear approach is replaced by an incremental, iterative one. Instead of planning the whole project in advance, Agile enables the adaption of requirements during the whole project. This artice provides an introduction of each methodology, a comparison and examples of use, in order to facilitate the decision whether Agile or Waterfall is more suitable for the next project.
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Waterfall Methodology
The lifcycle model which is today known as traditional or Waterfall model was first described by Royce in 1970.[1] It is called Waterfall model because of its sequential and down-flow characteristic where the phases analysis, design, implementation, testing and release are processed consecutively downwards.[2] Each phase of the Waterfall model is processed in order without any overlapping and within a specified time period. Once a phase is completed there is no going back to a privious phase as it will be frozen.[3]
Analysis
In this phase all the requirements and customer needs of the desired system or product are gatherd and recorded in detail in a specification document.[2] This document will be used as input in the design and implementation phase. The requirements of the product should be clear before moving to the next phase as changes in requirement can not be adapted later in the process.[3]
Design
The outcome of the design phase are a specified hardware and a virtual overview of the desired system or software.[3]
Implementation
The actual development of the system starts in the implementation phase. The system is therefor divided in small sub units which are tested by the developers before forwarding them to the testing phase. A quality gate checklist helps to control if there is a deviation from the requirements, planned time-line and product scope.[4]
Testing
In this phase the sub units are integrated to one working system which is tested regarding quality and functional aspects. The collected measures of performance are used for the decision whether the system is ready for the relase. In order to ensure that the outcome of the project meets the customers' requirements the tested system is reviewed according to a checklist. [4]
Release
The product gets prepared for beeing released into the market or delivered to the customer (including installation instructions of the system for customers and user-guides). There is another quality gate in order to check if the final product meets the customer and quality requirements and wheter it is delivered in time. [4]
Maintenance
After releasing the product in the customer environment there can occur problems in the products performance. Hence, the company must provide maintenace in order to solve this issues.[4]
Pros
- All requirements are clearly documented before the development of the product starts
- Each phase is finished in a specified period of time before moving to the next phase
- Waterfall is simple to implement as it is a linear model
- The amount of resources needed for implementing the waterfall methodology is minimal
- Each phase follows appropriate documentation in order to ensure the quality development [3]
Cons
- you cannot return to a privious phase. If the design phase fails the project might become very complicated in the implementation phase.
- if a customer wants to change requirements of the product they cannot be implemented in the current development process
- Even small changes or errors in the finalized product might be very costly and cause a lot of problems [2]
Agile Methodology
Pros
- Changing requirements can be implemented at any phase of the process due to short development cycles
- A working product can be developed very quickly [2]
- Continous improvement enables fast and high quality delivery
- Continious dialogue between the customer and the development team ensures immediate user feedback
- The Agile methodology attaches great importance to teamwork as it requires frequent communication and face-to-face interactions. [5]
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