Software development occurs in context of system development process: Desired characteristics are not well known in advance. Using prototyping, the analyst can provide a practical demonstration of the relevant parts of the software to the client. This ensures better communication about requirements, and a mechanism through which to get feedback. Prototyping interactive systems enhances communication regarding suitability of human-computer interfaces. Further, they can be used to demonstrate technical, economic, & political feasibility.

In prototyping, we are interested in the PROCESS rather than the PROTOTYPE.

Prototyping Steps:

Functional Selection: range of functions never same as final software product.

Construction: emphasis on intended evaluation disregarding data validity.

Evaluation: need a test plan & evaluation resources & all relevant user groups.

Further Use: Throwaway learning vehicle versus component of a larger system.

Types of Prototyping

Exploratory: Clarify information requirements & desirable features & alternative design possibilities.

Analysts knows little about the business & user knows little about what is possible with computers. Make explicit what users like & dislike & how it should be taken into account into the target system.

The requirements & functional analysis of the prototype language are different from the production language, and the prototype effort should be minimized.

Experimental: Test the adequacy of proposed solutions before large-scale implementation.

This is a proposed system is tried out!

A full functional simulation prototype exhibits all functions of the target system - system may not work as a production system due to inefficiencies or data validation. A partial functional simulation prototype used to test a proposed algorithm. A human interface simulation prototype looks like a real system but there may not be real data behind the program. Skeleton Prototyping involves a few system functions prototyped as being relevant & users perform some normal work tasks & extend experiences to other not prototyped tasks.

Evolutionary: Adapting system gradually to changing requirements.

System context evolves & new requirements emerge & the application once in use transforms its usage context & causes new requirements to emerge.

Incremental Development & stepwise extension of the system & (re)design, (re)implement, (re)evaluate.

Modular Design & Dialogue Design & Simulation.

Tools: High-level Languages & data base management systems & dialogue definition systems & specification languages & symbolic execution systems.

Dangers: Badly thought out designs & never ending development & sabotaged system development.