Prototyping

When a prototype is generated, the developer produces the minimum amount of code necessary to clarify the requirements or design elements under consideration. No effort is made to comply with coding standards, provide robust error management, or integrate with other database tables or modules. As a result, it is generally more expensive to retrofit a prototype with the necessary elements to produce a production module then it is to develop the module from scratch
using the final system design document.

For these reasons, prototypes are never intended for business use, and are generally crippled in one way or another to prevent them from being mistakenly used as production modules by end-users.

Advantages

• The software designer and implementer can obtain feedback from the users early in the project.
• The client and the contractor can compare if the software made matches the software specification, according to which the software program is built.
• It also allows the software engineer some insight into the accuracy of initial project estimates and whether the deadlines and milestones proposed can be successfully met.

Disadvantages

• Often clients expect that a few minor changes to the prototype will more than suffice their needs. They fail to realise that no consideration was given to the overall quality of the software in the rush to develop the prototype.
• The developers may lose focus on the real purpose of the prototype and compromise the quality of the product. For example, they may employ some of the inefficient algorithms or inappropriate programming languages used in developing the prototype. This mainly due to laziness and an over reliance on familiarity with seemingly easier methods.
• A prototype will hardly be acceptable in court in the event that the client does not agree that the developer has discharged his/her obligations. For this reason using the prototype as the software specification is normally reserved for software development within an organisation.

When to use this model

• Prototyping is very effective in the analysis and design of on-line systems.
• Systems with little user interaction, such as batch processing or systems that mostly do calculations, benefit little from prototyping. Sometimes, the coding needed to perform the system functions may be too intensive and the potential gains that prototyping could provide are too small.
• Prototyping is especially good for designing good human-computer interfaces. "One of the most productive uses of rapid prototyping to date has been as a tool for iterative user requirements engineering and human-computer interface design."