SDLC MODEL

Group no. 3
The waterfall methodology. Question 3

The history of the waterfall model
The waterfall model which is also referred as a linear sequential life cycle model was the first model to be developed. The waterfall model is a sequential design process used in software development processes in which progress is seen as flowing steadily downwards(like a waterfall) through the phases of conception, initiation, analysis, construction ,testing, production/implementation and maintenance. The waterfall model creation originates in the manufacturing and construction industries. Since there was no formal software development methodologies existed at the time, this hardware oriented model was simply adapted for software development. Stages of the waterfall methodology The waterfall model stipulate that one should move to a phase only when its preceding phase is completed and approved. All these phases are cascaded to each other in which progress is seen as flowing steadily downwards (like a waterfall) through the phases. The next phase is started only after the defined set of goals are achieved for previous phase and it is signed off, so the name "Waterfall Model". In this model phases do not overlap.
The stages to be followed are as follows.
Design resulting in the Software architecture
Construction (implementation or coding) resulting in the actual software
Integration
Testing and debugging
Installation
Maintenance

The sequential phases in Waterfall model are:
Requirement Gathering and analysis: All possible requirements of the system to be developed are captured in this phase and documented in a requirement specification doc.
System Design: The requirement specifications from first phase are studied in this phase and system design is prepared. System Design helps in specifying hardware and system requirements and also helps in defining overall system architecture.
Implementation/construction: With inputs from system design, the system is first developed in small programs called units, which are integrated in the next phase. Each unit is developed and tested for its functionality which is referred to as Unit Testing.
Integration and Testing: All the units developed in the implementation phase are integrated into a system after testing of each unit. Post integration the entire system is tested for any faults and failure
Deployment of system: Once the functional and non-functional testing is done, the product is deployed in the customer environment or released into the market.

Maintenance: There are some issues which come up in the client environment. To fix those issues patches are released. Also to enhance the product some better versions are released. Maintenance is done to deliver these changes in the customer environment.

Techniques used in waterfall methodology
The techniques used in waterfalls method are as follows;
Various flow charts, which might, for example, help the analyst trace the flow of documents through a department.
The organization chart showing the reporting structure of people in a company department.
Manual documents specification, giving details of documents used in the manual system,
Grid charts showing how different components of the system, such as people and machines, interact with each other.
Discussion records on which the notes taken at interviews could be recorded.
File and record specifications describing in former case all the data items in record including their names and description, size, format, and possible range of values.
System that have been developed using waterfall methodology
Library management system.
Airline reservation system.
Hospital management system
Payroll system A critique of the waterfall methodology. Advantages of waterfall methodology.
The advantage of waterfall development is that it allows for departmentalization and control. A schedule can be set with deadlines for each stage of development and a product can proceed through the development process model phases one by one.
It is easy to manage due to the rigidity of the model – each phase has specific deliverables and a review process In this model phases are processed and completed one at a time. Phases do not overlap.

The project requires the fulfillment of one of the phase, before proceeding to the next. Therefore if there is fault in the software it will be detected during one of the initial phases and will be sealed off for correction.
A lot of emphasis is laid on paperwork in this method as compared to the newer methods. When new workers enter the project, it is easier for them to carry on the work from where it had been left. The newer methods don’t document their developmental process which makes its difficulty for a newer member of the team to understand what step is going to follow next. The waterfall model is a straight forward method and lets one know easily what stage is in progress.. Disadvantages of waterfall methodology
Once an application is in the testing stage, it is very difficult to go back and change something that was not well-thought out in the concept stage. This make it risky.
Many software projects are dependent upon the external factor, out of which the client for which the software is being is the biggest factor. Its happen a lot times, that the client changes the requirement of the project, thereby influencing an alteration in the normal plan of the construction and hence the functionality as well. The waterfall model doesn’t work well in a situation like this as it assume no alteration to occur once the process has started according to plan. If it occur its means that the design will be required to start the process afresh.
A huge amount of time is also wasted, for instance, we know that phase ii cannot be executed until phase I has been successfully completed, so while the designers are still designing the software, time of the builders is completely wasted
The testing periods comes quite late in the developmental process, whereas in various other developmental programs the designs would be tested a lot of time and money has not been wasted.
References
http://istqbexamcertification.com http://www.tutorialspoint.com/sdlc/sdlc_waterfall_model.htm http://istqbexamcertification.com/wp-content/uploads/2012/01/Waterfall-model.jpg.
Donald Yeates and Tony Wakefield (2004) System Analysis and Design, Pearson education limited New York.

References: http://istqbexamcertification.com http://www.tutorialspoint.com/sdlc/sdlc_waterfall_model.htm http://istqbexamcertification.com/wp-content/uploads/2012/01/Waterfall-model.jpg. Donald Yeates and Tony Wakefield (2004) System Analysis and Design, Pearson education limited New York.