Introduction to Information Systems Models and Methodologies - High Level Models and Methodologies for Information Systems - page 5

Fig. 1.2 Waterfall model (adapted from Balaji and Murugaiyan 2012 )

development under the perspective of traditional methodologies, with an emphasis
on the process, rigorous documentation, and self-contained stages. It was the rst

approach to SDLC in research.
The second type of SDLC comprises the incremental-type models. The incre-
mental model contradicts the waterfall principle of developing a system in a single-
pass process, with rigorous documentation and an extensive testing stage, to pro-
duce a

final, fully usable product in the end. Incremental models instead propose
developing a system in successive builds or increments. With each build, the system
is designed and developed, and a working version or prototype is implemented.
Users can then test it actively, within working contexts, and provide valuable
feedback. This feedback will then be used as a starting point for the next build.
With each successive build, the system becomes more complete, more functional,
and closer to what the users intend (Massey and Satao 2012 ).
Most models of SDLC can be considered variants of the waterfall model, the
increment model, or a combination of both. By introducing innovative concepts
within the structure of the original models, or by bringing together the strong points
of each one, researchers have attempted to build ideal models of SDLC for many
years, resulting in a great variety of different approaches.
The V-model was an adaptation of the waterfall model that attempted to
emphasize the testing stage, by proposing that each stage of the process entails a
certain type of testing activity. It was presented in the shape of a V. The rst

sequence of events moves downward like the waterfall model, from analysis of
requirements, to high- and low-level design, and coding. Once coding is complete,
and a new sequence of actions moves upward, comprising all the different testing
phases that should be followed: unit testing, integration testing, system testing, and
acceptance testing (Balaji and Murugaiyan 2012 ).