un Systeme
ormation soit
> le Système
Méthodes de
:'veloppement
veloppement
la procédure
Benefits from Methodologies should include high quality
products which are easy to maintain and upgrade, better
control during the design process, reduction time to
completion and lower costs of developments.
Unstructured Methodologies
Generally referred to as "Conventional Approach" in most
texts, they where prevalent in the 1970s. The philosophy
behind these Methodologies is visualised as shown in
Figure 1.
^N
TOP ( STRATEGIC )
MANAGEMENT
IGNORED BY
COMPUTER
MIDDLE ( TACTICAL )
MANAGEMENT
OPERATIONS
MANAGEMENT
(a). Failure to meet all Organisational needs.
WHAT FILES WILL
HOLD THE NECESS-
ARY STATIC DATA?
des
WHAT DATA WILL
WHAT ARE THE WHAT PROCESSES
A] WILL LEAD TO
REQUIRED
v] THAT OUTPUT
OUTPUTS ? BEING ARCHIEVED?
BE REQUIRED AS
RAW INPUT?
(b). Output Driven Design.
Figure 1 A Window on Unstructured Methodologies
(Adapted from Avison & Fitzgerald)
m Unstructured Methodologies were unsatisfactory due
0:
Failure to meet the needs of management, instability and
Inflexibility, user dissatisfaction, problem of documentation,
incomplete Systems, little or no control over the quality of
the design, and lack of an objective criteria with which to
judge whether the critical activities of analysis and design
were carried out properly [Yourdon, 1988].
These create concern for:
Low productivity, low quality, long development cycles,
increasing costs of development and maintenance of
Systems, and thus create the need for Structured
Methodologies [Paresi, 1991].
The concern for more productive methods for the
development of information systems has therefore
tremendously increased during the last two decades. A
wealth of research has addressed the problem of
developing efficient and effective Information Systems. Four
approaches to development methodologies have emerged
from research and experience; these are the formal
methods, the structured methods, the soft methods, and
the socio-technical methods. In practice, any development
is a combination of these different approaches; only
Structured Development Methodologies will be considered
here.
Structured Systems Development Methodologies
Necessity and Basic Features:
Given the generic objectives of Methodologies as stated
earlier, it is obvious that conventional approaches fail
particularly when Systems become more complex.
Structured Methodologies seek to address these failures as
outlined above with particular consideration to the reduction
of the cost of rectifying changes in user requirements. Such
changes would remain minimal if these requirements are
considered extensively during the analysis phase [Cutts,
1991]. They also seek to mirror organisational patterns
faithfully during implementation [Ward,1984]. Some of the
fundamental features of Structured Methodologies include:
(1) A Top-Down approach with a strict philosophy of
separating the conceptual System from the physical
System. Much effort is put developing the conceptual
system during which the analyst gets an overall grasp
of the System, breaks the picture down in manageable
details, with a productive use of time.
(2) They avoid the duplication of efforts and waste of
resources, thereby reducing the volume of work and
speed up the overall System Development process.
(3) Much of the documentation, which is in the form of
diagrams and systems encyclopedia (or data
dictionary), are better understood by non-technical
users, and clear thinking is encouraged.
(4) By encouraging standardized methods, another
designer can easily assimilate the steps, and
System maintenance becomes less cumbersome.
(5) The Techniques and Tools are not ‘doctrinal’ or
inflexible and force the analyst to ask questions to
users, and of himself, thereby minimising wrong
assumptions during design.
(6) Most parts of the analysis and design can be
developed, maintained and held on computer
systems (CASE tools), easing the work of
documentation.
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