Explain the Spiral model with the aid of diagrams.?

this is one of the process models used in the software development life cycle. for example there is the Waterfall model. Please help me with the Spiral model and any diagrams.also give me the advantages and disadvantages of the Spiral model.

The spiral model has several advantages. Among them is the emphasis on alternatives and constraints. This reinforces the reuse of existing software and forces software quality to be a specific objective that can help reduce the testing necessary for the project. Another advantage is that the model is risk-driven. This allows a team to avoid problems and potential dead-ends along the road leading to the final product. Finally, another advantage is that this model incorporates the many features of other models such as the Waterfall and Rapid Prototyping models.

The life cycle process to be used by Team UMT will be the spiral model. The underlying principle behind this model is to minimize risks through the use of prototypes and other means such as incremental risk analysis. At each phase of the project such as Specification, Design, and Implementation, there is a risk analysis and possible use of prototyping to evaluate each stage of the project. As with most complex problems, there may be more than one solution. Each solution may have its own advantages and disadvantages, but would be a correct solution none the less. This project is no exception. By using the spiral model, Team UMT can guide the project toward the 'best' solution for the client.
The spiral model has several advantages. Among them is the emphasis on alternatives and constraints. This reinforces the reuse of existing software and forces software quality to be a specific objective that can help reduce the testing necessary for the project. Another advantage is that the model is risk-driven. This allows a team to avoid problems and potential dead-ends along the road leading to the final product. Finally, another advantage is that this model incorporates the many features of other models such as the Waterfall and Rapid Prototyping models.
The spiral model also has its disadvantages. One disadvantage is the fact that the model is risk-driven. This requires the developers to have sufficient foresight to identify risks and potential dead-ends to the project. Not only do the developers need to identify the risks but also to resolve them. Another disadvantage is the fact that a thorough risk analysis is not done at the beginning of the project, but in small increments along the way. Often times, a client may not be willing to commit to a project unless all risks are known and dealt appropriately

A diagram of the spiral model is shown below.