A prototype is used to demonstrate a model or a limited- or non-working version of a product to stakeholders with the intention of validating that it meets their requirements. It is used to solicit more requirements or to alter any requirements that may have changed or been miscommunicated to designers.

The two common types of prototyping are throw-away and evolutionary (or functional) prototyping. The first approach discards the prototype once it is used for demonstrative or requirements elicitation purposes, whereas the latter approach uses an initial version of a product that is evolved and improved on.

Some examples of different forms of prototyping include the following:

• A proof of concept model: This type of prototype models the design of a system and doesn't show the workflow, visual aspects, or materials used.
• A form study: This type of prototype only illustrates the look and feel but doesn't include any of the functionality.
• A usability prototype: This type of prototype is designed to allow you to see how a user interacts with it.
• A visual prototype: This type of prototype is used to only show the visual aspects of a solution and does not include any functionality.
• A functional prototype: This type of prototype includes the functionality, workflow, and qualities of a system in development.

Any of the preceding forms of prototyping can be applied to elicit, validate, or explore requirements with stakeholders.

Some examples of commonly used methods for prototyping are as follows:

• Storyboarding: This shows the sequence of activities of a solution in a visual and textual pictorial format.
• Paper prototyping: This is drawing a process or user interface with a pencil and paper.
• Workflow modeling: This shows a sequence of steps (usually human-centric).
• Simulation: This demonstrates a solution or components of a solution (for feedback).

These methods of prototyping are used in either a formal or informal manner to expedite and complete the requirements elicitation activities.