System Analysis Models
EVOLUTIONARY MODELS
1-Waterfall model
It is a cascading design process and is often used in software development processes, and progress in the workflow is in the form of fixed pieces flowing from top to bottom (like a waterfall) and for this reason it is called this and from the following stages: first knowing the system requirements, then starting the analysis, Then the design process, construction, testing, production, implementation and maintenance. The waterfall model arises in manufacturing and construction, but changes within physical environments are costly and costly, if not impossible. With no possibility to present the necessary software development process at the time, this model was simply adapted to software development
History of the model
The first conference to undertake the process of using similar stages in software engineering by (Herbert D. Bennington) was held at a symposium on the advanced programming methods of digital computers in 1956. This was a presentation on software development for SAGE. In 1983, the paper was republished with a presentation by (Bennington), noting that this process was not from top to bottom but relied on the original model .. The first process was to describe the waterfall form officially as an article by Winston Royce, which he presented in 1970, though Royce did not use the term waterfall in that material. Royce viewed this model as faulty and unable to work; This method is used in writing about software development to describe a critical view of commonly used software development practices. The earliest use of the term "waterfall" may have been in Bill and Thayer's paper in 1976
Waterfall model stages
Requirements: It is the stage of collecting potential requirements for the application and systematic analysis and is written on in a document
Analysis: It is the process by which data are collected on the problem
Design: It is the stage of designing solutions to collected problems
Building: It is the stage of building a plan with clear goals to solve the problem
Testing: It is the process of testing and experimenting with the product that we have chosen whether or not it works
Operations: This stage includes not only the deployment of the application, but also subsequent support and maintenance
Pros of the waterfall model
The model is easy to understand
Easy to manage
The stages handle another stage when they are completed
This model allows the work to be divided into a group of small projects for easy understanding
This model is preferred for quality projects
negatives of model
It contains a large percentage of risks
Not suitable for complex projects
Not suitable for high risk
Not suitable for long projects
2- Spiral model
The spiral model combines the elements of models and design that are available on a group of stages, and this is done by trying to combine the advantages of those concepts from top to bottom and from bottom to top. Also known as the (spiral development model), it is the method of developing systems used in information technology. This model combines the characteristics of the models and the waterfall model, which was explained in the first paragraph. The spiral model was invented for mega projects because the waterfall model did not suit it, or costly and complex projects. It cannot be confused with the spiral model of modern systems architecture that uses dynamic programming (mathematically not a type of programming!) Which was designed to improve the architecture system before making design decisions by programmers that would cause problems
History of the model
In his 1986 essay, Barry Boheme defined the vortex model by "the spiral model of the software development process and its improvement as well" and the reason is to identify unexpected errors and problems and this model was not the first model to discuss iterative development. The repetition process usually takes from 6 months to two years. Each stage begins with the design goal and ends with the customer (who may be internally) reviewing the progress made up to this point. Analysis and effort engineering are applied at every stage of the project, taking into account the ultimate goal of the project
Stages of the spiral model
1. Define requirements
2. Problem analysis
3. Introduce problem solutions (design)
4. Confirm the specifications
5. Design implementation
6. make a test
7. Maintenance errors
The positives of the spiral model
• Suitable for large projects.
• Fully documented.
• The ability to add additional requirements to the system.
• Significant risk analysis, which helps reduce the possibility of risk occurring.
The downsides of the spiral model
• Not suitable for small projects. Waterfall model preferred.
• The risk analysis process requires specialized expertise
3-prototype model
The prototype is not new, but it was one of the innovations of information systems. It used this system from an old era, where the military used sand paintings in modeling battles and structural engineers used in modeling bridges. After the procedural language calculators appeared, which called the third generation, then the prototype gained strength after the emergence of The fourth generation, and then the emergence of software packages such as CASE and SADAT, which prompted many systems analysts for the life cycle of information systems with the initial model method and the most important reasons for creating this model were to build this model to understand system requirements and also was developed on the basis of financial requirements. and The customer can give an opinion about the system
Pros of the prototype
• What distinguishes this system is that it gives the user an effective role in developing this system.
• Errors within this system can be addressed early.
• The ability to easily identify system deficiencies.
Cons of the prototype
•The complexity of the prototype can be increased by doing an expansion of the system beyond the original plans.
Incremental model
TERATIVE ENHANCEMENT MODEL
This incremental model has the same specifications available as the waterfall model stages, but with fewer restrictions
Because it combines the elements of the waterfall model with an iterative method whereby each linear sequence of increases is produced within the program and most of the time the first increase is an essential product and the first product is used by the customer and based on the evaluation results a plan for the increase is developed
RAPID APPLICATION DEVELOPMENT MODEL
This model was developed in 1980 and this model relies on a large group of short iterative software development courses. RAD is an appropriate solution for slow models as it is high speed and the duration of development is between 2 to 3 months. This model focuses on developing rapid applications and collecting customer requirements accurately through A group of experts
What are the stages of RAD
• Requirements Planning
• User Design
• Construction
• Cutover
advantages of RAD
• Understand changes that may occur in requirements
• The ability to track the development and progress of work
• Receive customer feedback continuously from the customer
• Reducing development time
Disadvantages of RAD
• Requires budget for tools utilities
• Not suitable if there are high technical risks
• It is used only on partitionable systems
• It requires the involvement of users
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