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Software Development Models Transcription

Welcome to our software development methods module. Traditionally, software has been developed using the waterfall method, which is a pervasive method for measuring twice and cutting once. This method has discreet phases of development, each phase requiring a formal review, approval, and documentation of the task before you can flow down to the next phase, just like a waterfall.

The first phase is the requirements definition, where you conduct an investigation to determine what the needs of your client are. The second phase is the system and software design phase, where an analysis is conducted to determine exactly how the system should function. The third phase is the implementation phase and unit testing, where the software is logically designed.

The fourth phase is the integration and system testing phase, through where the physical design of the system is conducted. The fifth phase is the documentation, implementation, and operational maintenance phase, where you continue to make sure that the software is functioning properly and is completely documented. And face six is the end of life phase where the retirement of the system is conducted.

The waterfall method is most suited for large, long-term projects. For the CISSP examination, you should remember that the waterfall method requires each phase to be completed before moving to the next phase, just like a waterfall. Here is a diagram of the waterfall model. You can see we begin with feasibility phase, moving onto the analysis phase, and then to the design phase and so on.

Once we reach the maintenance phase, we can move back to the beginning in case additional changes need to be made to the software or any improvements need to be added. This is a linear sequential life cycle model, meaning that it must move in order. The model does not allow you to skip any steps and does not allow you to change anything in a previous step without starting over.

The prototyping model is where you test the concepts. This is successful generally because of customer feedback as part of the agile model. The users, managers, and IT staff members will discuss and agree upon business needs and the scope of the project. This is important to develop an understanding of the requirements for the system and the constraints that you'll need to follow without actually developing a final product.

You'll share your prototypes with the customer for feedback. Here the users get to interact with the system and you can develop models and prototypes that will represent the system's processes, inputs, and outputs. Rapid application development is a form of prototyping based on strict time limits that may be implemented for each phase.

Joint analysis development is where the developers work directly with the users to create an application that's working and meets their needs. The spiral model is a model with multiple cycles that are repeated. It's a combination of the waterfall and prototyping modules with an additional risk assessment. In each phase, also known as a quadrant, the design objectives and the associated risks are defined and analyzed through the use of the prototypes that the client gets to review.

During each spiral iteration, something is accomplished. Each iteration is designed using the waterfall model and the first spiral is actually a proof of concept, so you're trying to get A and B. You'll then do a risk assessment after each step to determine if the development is ready to continue.

During the second spiral, or version two, you'll set the expectations and let the customer know that you can do A,B,C, and D. In the third spiral, version three, you'll then add more of the customer's wants and desires into the program. And during the fourth spiral, or version four, you'll determine if the application is ready for acceptance testing.

For the CISSP examination, you should remember that the spiral model has multiple repeated cycles and is a combination of the waterfall and prototyping model with a risk assessment. The agile model focuses on getting a program up and running as soon as possible. This model requires close collaboration between business experts and your programming team, in order to determine the needs and develop a solution.

Frequently you will be delivering new deployable business value and you'll have face to face communication to speed up the knowledge sharing process. The agile model uses a storyboard in order to increase communications and involves a few tight self-organizing teams. The agile model also provides ways to craft code and your teams so that your inevitable requirements churn is not a crisis, but a way to prototype.

The focus here is on the individuals and the interactions rather than a historical focus on structured processes and tools. Your goal is to get the software working as soon as possible without worrying about comprehensive documentation and security. You will worry about customer collaboration rather than contract negotiation and you will respond to changes quickly rather than following a predefined structure.

For the CISSP examination you should remember that the agile model focuses on getting programs in service as soon as possible and is less focused on security than other modules. Extreme programing is one of the agile software development processes that focuses on team work. Planning is based on user's stories or daily actions.

It's a flexible software development model based on respect, communication, simplicity, feedback, and courage. You will have lots of iterations with this model with real time editing possible if necessary. Programmers will typically work in pairs and your development time will be very short but very intense. With the extreme programing model you will write the code to the agreed upon standards and test it to make sure that it is working properly. The clean room model for software development is where you trust your developer to write good code and get your software working correctly the first time. Statistical use testing is used to find high impact errors. With this model, producing unique software with a certifiable level of initial security and reliability will take a long time.

And it is important to document that this was an original product that was not stolen. When you focus on the clean room process, you are focusing on defect prevention rather than removing defects. You will have small teams working together on iterations and this model focuses on not releasing a buggy piece of software and then constantly patching it to improve the problems.

The name comes from clean rooms, which are used in the preparation of integrated circuits or ICs. For the CISSP examination you should remember that the clean room model focuses on writing code correctly the first time and preventing defects rather than fixing them later. Computer aided software engineering or CASE is an integrated development environment, which is a term for a lot of different automated productivity tools that can help your project managers, programmers, and analysts during the development of a piece of software.

It allows for rapid prototyping, less manual coding, which means less errors, automating repetitive tasks, and also provides debuggers, code analyzers, and version control tools. This software can help you to automate the process of checking code in and out so that your developers can work on it. The tools built in to case will help you to document as you move throughout the process rather than trying to document at the conclusion of the development, which is more common.

Here development is quicker and more accurate because you're using computer aided tools. For the CISSP examination you should remember that CASE can be very helpful, and that most importantly it allows you to document as you go. So that you can have proper documentation at the conclusion of the development process instead of having to go back and develop the documentation after the software is already up and running.

This concludes our software development methods module. Thank you for watching.