The Software Development Life Cycle - Software Testing: Testing Across the Entire Software Development Life Cycle - page 57

and performance criteria. The evaluation can be made by users and such unbiased
third parties as internal auditors and consultants. The fi ndings of these evaluations
can determine whether additional systems work is necessary.
Over time as the system is used, both formal and informal additional evalua-
tions can be made. These evaluations form the basis for future redevelopment and
reengineering projects.
2.11 PUTTING PHASED DEVELOPMENT IN
PERSPECTIVE
The classical SDLC was not that bad from a logical standpoint. It is hard to
find fault with a repeatable sequence of planning, analysis, design, and imple-
mentation that worked. The big weakness was that the continual need to re-
peat stages was not anticipated in a proactive way and had to be handled in
a reactive way. Prototyping excels when it comes to the iterative design and
development because that is the main idea of that methodology. The PDM is a
blending of the logical sequence of the classical SDLC and proactive iterative
prototyping. The main strength of the PDM is the fact that it subdivides the
system into modules and then regards each as a separate phase of Analysis,
Design, and Preliminary construction. It is an extremely flexible methodology
that is applicable to all but exceptionally small projects, where prototyping can
fulfill the need.
2.12 SUMMARY
An information system methodology is a recommended way to develop an informa-
tion system. This methodology is known as an SDLC. SDLCs have evolved from
classical to prototyping to RAD to phased development.
Phased development consists of six stages: Preliminary investigation, Analysis,
Design, Preliminary construction, Final construction, and Installation. The Analy-
sis, Design, and Preliminary construction stages are repeated for each subsystem,
or module, of the system being developed. Each sequence of analysis, design, and
preliminary construction for a module is called a phase.
During Preliminary investigation, an enterprise analysis is conducted; system
objectives, goals, and performance criteria are defi ned; system and project risk are
evaluated; and system and project feasibility are evaluated. Findings are reviewed
with users in JAD sessions and approval to proceed is received.
During the analysis stage, functional requirements are analyzed using a variety
of data gathering techniques and are then documented. During the Design stage, the
logical design is developed by identifying feasible designs, evaluating them, con-
ducting JAD sessions to confi rm designs and evaluations, and selecting the best.
Six types of design include user interface, procedure, data, interfaces with other
systems, controls, and software.