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Waterfall Model

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Ali Saffar

on 12 November 2015

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Transcript of Waterfall Model

Waterfall Model
Winston Royce
1970

Requirements
Design
Implementation
Verification
Maintenance
Waterfall model

has been structured on multiple phases especially to help out the software construction companies to develop an organized system of construction. By following this method, the project will be divided into many stages thus easing out the whole process. For example you start with Phase I and according to this model, one only progresses to the next Phase once the previous one has been completed. This way one moves progressively to the final stage and once that point is reached, you cannot turn back; similar to the water in a waterfall.
waterfall model
has been structured on multiple phases especially to help out the software construction companies to develop an organized system of construction. By following this method, the project will be divided into many stages thus easing out the whole process. For example you start with Phase I and according to this model, one only progresses to the next Phase once the previous one has been completed. This way one moves progressively to the final stage and once that point is reached, you cannot turn back; similar to the water in a waterfall.
Winston W. Royce
(1929–1995) was an American computer scientist, director at Lockheed Software Technology Center in Austin, Texas, and one of the leaders in software development in the second half of the 20th century. He was the first who described the Waterfall model for software development, although Royce did not use the term "waterfall" in that article, nor advocated the waterfall model as a working methodology.
Definition Study - Analysis:
During this phase research is being conducted which includes brainstorming about the software, what it is going to be and what purpose is it going to fulfill.
Basic Design:
if the first phase gets successfully completed and a well thought out plan for the software development has been laid then the next step involves formulating the basic design of the software on paper.

Technical Design / Detail Design:
After the basic design gets approved, then a more elaborated technical design can be planned. Here the functions of each of the part are decided and the engineering units are placed for example modules, programs etc.
Construction - Implementation:
In this phase the source code of the programs is written.

Testing:
At this phase, the whole design and its construction is put under a test to check its functionality. If there are any errors then they will surface at this point of the process.
Integration:
in the phase of Integration, the company puts it in use after the system has been successfully tested.
Management and Maintenance:
Maintenance and management is needed to ensure that the system will continue to perform as desired.
Advantages of the Waterfall Model

Design errors are captured before any software is written saving time during the implementation phase.
Excellent technical documentation is part of the deliverable and it is easier for new programmers to get up to speed during the maintenance phase.
The approach is very structured and it is easier to measure progress by reference to clearly defined milestones.
The total cost of the project can be accurately estimated after the requirements have been defined (via the functional and user interface specifications).
Testing is easier as it can be done by reference to the scenarios defined in the functional specification.
The project requires the fulfillment of one phase, before proceeding to the next. Therefore if there is a fault in this 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 it difficult 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.
The Waterfall method is also well known amongst the software developers therefore it is easy to use. It is easier to develop various software through this method in short span of time.
Disadvantages of the Waterfall Model

Clients will often find it difficult to state their requirements at the abstract level of a functional specification and will only fully appreciate what is needed when the application is delivered. It then becomes very difficult (and expensive) to re-engineer the application.
The model does not cater for the possibility of requirements changing during the development cycle.
A project can often take substantially longer to deliver than when developed with an iterative methodology such as the agile development method.

Many software projects are dependent upon external factors; out of which the client for which the software is being designed is the biggest factor. It happens a lot of times, that the client changes the requirement of the project, thereby influencing an alteration in the normal plan of construction and hence the functionality as well. The Waterfall Model doesn’t work well in a situation like this as it assumes no alteration to occur once the process has started according to plan.

If, for instance, this happens in a Waterfall Model, then a number of steps would go to waste, and there would arise a need to start everything all over again. Of course this also brings about the aspect of time and money which will all go to waste. Therefore this method will not at all prove to be cost effective. It is not even easy to take out the cost estimate of each step, as each of the phases is quite big.

There are many other software developmental models which include many of the same aspects of the Waterfall model. But unlike the Waterfall model, these methods are not largely affected by the outside sources. In the waterfall model, there are many different people working in the different phases of the project like the designers and builders and each carries his own opinion regarding his area of expertise. The design, therefore, is bound to be influenced; however in the Waterfall model, there is no room for that.

The other negative aspect of this model is that a huge amount of time is also wasted. For example if we study any software development process, 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.
Another disadvantage of this method is that the testing period comes quite late in the developmental process; whereas in various other developmental programs the designs would be tested a lot sooner to find the flaw at a time when a lot of time and money has not been wasted.
Elaborate documentation during the Waterfall method has its advantages, but it is not without the disadvantages as well. It takes a lot of effort and time, which is why it is not suitable for smaller projects.
Due to the various disadvantages a lot of other modified versions of this model have also been put forth and some of these are mentioned below:

Royce Model
Although not documented as the “Waterfall Model,” Winston W. Royce is credited with the first formal description of what we no know as the Waterfall Model in 1970. In his original definition, the model consisted of the following steps: Requirements specification, Design, Construction (or coding in today’s terms), integration, testing and debugging, installation, and maintenance.

Sashimi Model
Sashimi is a true modified version of the Waterfall model. The phases are somewhat the same as in the Waterfall Model; only this time the phases are overlapping each other which present many advantages. For example the time won’t be wasted because before Phase I would be completed, Phase II would already be underway. Moreover, since they overlap, so one can return to the previous step if desired.

Aorta Lifecycle Model
The difference in this model is that they rely a lot on the feedback which comes from other phases before progressing onto the next.

V Waterfall Model
The V Waterfall Model relies on a linear software developmental program which stresses on balanced development more than anything else.
یسنتایس
Requirements
Analysis
System
Design
Architecture
Design
Module
Design
Acceptance
Test Design
System
Test Design
Integration
Test Design
Unit
Test Design
Coding
Acceptance
Testing
System
Testing
Integration
Testing
Unit
Testing
This is the first step in the verification process. It is in here that the project and its function is decided. So a lot of brainstorming and documentation reveals what all will be required to produce that program or product. During this stage the employees are not going to discuss how it is going to be built; it is going to be a generalized discussion and a user requirement document is put forth. This document will carry information regarding the function of the system, performance, security, data, interface etc.
Like the name of the phase suggests, here the possible design of the product is formulated. It is formulated after keeping in mind the requirement notes. While following the documents, if there is something that doesn’t fit right in the design, then the user is made aware of it and changes are accordingly planned. Diagrams and data dictionary is also produced here.
The architecture design, also known as the computer architecture design or the software design should realize the modules and the functionality of the modules which have to be incorporated.
In the module design, the architectural design is again broken up into sub units so that they can be studied and explained separately. The units are called modules. The modules can separately be decoded by the programmer.
A unit in the programming system is the smallest part which can be tested. In this phase each of these units are tested.
In this phase the separate entities will be tested together to find out the flaws in the interfaces.
After the previous stage of interface testing, in this phase it is checked if the system meets the requirements that have been specified for this integrated product.
In the acceptance test, the integrated product is put against the requirement documents to see if it fulfills all the requirements.
V Waterfall Model
Paul E. Brook
1986
Waterfall model

has been structured on multiple phases especially to help out the software construction companies to develop an organized system of construction. By following this method, the project will be divided into many stages thus easing out the whole process. For example you start with Phase I and according to this model, one only progresses to the next Phase once the previous one has been completed. This way one moves progressively to the final stage and once that point is reached, you cannot turn back; similar to the water in a waterfall.
waterfall model
has been structured on multiple phases especially to help out the software construction companies to develop an organized system of construction. By following this method, the project will be divided into many stages thus easing out the whole process. For example you start with Phase I and according to this model, one only progresses to the next Phase once the previous one has been completed. This way one moves progressively to the final stage and once that point is reached, you cannot turn back; similar to the water in a waterfall.
Winston W. Royce
(1929–1995) was an American computer scientist, director at Lockheed Software Technology Center in Austin, Texas, and one of the leaders in software development in the second half of the 20th century. He was the first who described the Waterfall model for software development, although Royce did not use the term "waterfall" in that article, nor advocated the waterfall model as a working methodology.
The V model
is a modified version of the Waterfall method. As opposed to the Waterfall method, this one was not designed in a linear axis; instead the stages turn back upwards after the coding phase is done so that it makes a V shape and hence the name – V Model. It was put forth by Paul E. Brook in 1986. Let’s look at the different stages, test processes, techniques, advantages and disadvantages of this method.
In the acceptance test, the integrated product is put against the requirement documents to see if it fulfills all the requirements.
Release Testing
It is in here that judgment has to be made if the product or software which is created is suitable for the organization.
a.s.sh
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