There are two types of prototyping incremental or

• There are two types of prototyping:
incremental or evolutionary and throwaway.

Incremental and Iterative Approach
• In incremental development, the product is
built through successive versions that are
refined and expanded with each iteration
– Three concepts underlie the incremental
approach:
• The Initialization Step
• The Control List
• The Iteration Step

Throwaway Approach
• In the incremental approach,
– the initial prototype is revised and refined
repeatedly until it becomes the final product.
• In the throwaway approach,
– the prototype is discarded after the stakeholders
in the development are confident that they have
arrived at the correct specifications and the
development on the “real” product can start.

Problems with Prototyping
• Unbalanced Architecture
– Since the main thrust of prototyping is towards the user interface, the
developers tend to include more and more functionality in the outer layers of
the information system, creating a distorted architecture
.
• The Illusion of Completeness
– Since the clients might not understand why the developers insist that a lot
more is to be done, the prototype may successfully present the user interface
for a complex functionality the feasibility of which is far from certain.
• Diminishing Changeability
– Since prototyping can leave little trace of how the development evolved,
modifying the application can resemble an archeological undertaking to piece
together a lost civilization.
• Prototyping can result in too little documentation or, more importantly,
too little modeling.

The Spiral Model
• The spiral model is a risk ‐ oriented lifecycle
model that breaks a software project up into
mini ‐ projects.

Rapid Application Development (RAD)
• Rapid Application Development is selecting
techniques, methods, practices and
procedures that would result faster
development and shorter schedules.

Characteristics of RAD
• Requirements Planning
– Aims at eliciting information and requirements from the senior people and
verifying the goals.
• Design
– The design phase begins once the top ‐ level requirements of the system are
identified. To discover more detailed requirements, RAD relies on Joint
Application Development (JAD) workshops
.
• Implementation
– Once the users approve the preliminary design, a detailed design of the
system is created and code is generated. Implementation phase is heavily
dependent upon CASE tools.
• Enhancements and Maintenance
– In the framework of RAD, a software is never completed until it is retired.
– there is no significant difference between development and maintenance.
(This position is in opposition to most SDLC methodologies.)

Agile Methodologies
• Agile methodologies aim at being adaptive
rather than predictive.

Extreme Programming (XP)
– A better ‐ known example of agile methods, and
one of the earliest ones, is Extreme Programming
(XP).