ALTERNATIVE APPROACHES TO SDLC
1. WATERFALL MODEL
Refers to a set of predefined steps followed in developing a system. The stages are inter-related
and happen in a cycle. The cycle constantly involves referring back and going back to what has
already been done. This cycle is a form of recycling, reworking of a previous stage in the light of
subsequent work.
This process of referring back is known as Iterative process.
The stages of a cycle include:
Feasibility study
Requirement specification
System Design
Programming
System testing and implementation
System operation and maintenance
2. PHASED APPROACH
It is an approach that specifies that one can develop and specify precisely a system in a top-
down approach. Successful phases elaborate the system in increasing detail with each phase
defining partial solution then calling for more detailed evaluation in the next phase. One phase
must be completed before the next phase start. A phase cannot be reviewed or repeated.
It has five phases namely:
Phase 1: Initiation of systems projects
This phase defines the user requirements of the new system
Provides a broad statement of user requirements in user words on what the user expects the
system to do thus set direction for the whole project
The major factors identified at this phase are
a) project goal
b) project bounds
c) Terms of reference for the project.
Phase 2: Detailed systems investigation and analysis
In this phase, it is necessary to find out more about what the systems problems are and what
users require of any new or changed system.
A number of output reports are generated at this phase i.e:
a. Analysis model: It describes the existing system
b. A requirement model: It specifies resources necessary to design the new system and
how it will work
c. A design model: It shows what and how it is expected to work
d. Project development plan: Defining the expected completion dates
e. Test plan: Defining any tests that are to be carried when and how for each detailed
requirement.
Phase 3: System design
Here the system analyst produces a design specification for the new system. He selects
equipment needed to implement the system. The requirements are translated into a suitable
system showing the flowcharts, structure charts, sub systems, procedures and functions.
Phase 4: System development
Individual system components design are built at this phase.. Programs are written basing on
the design procedures, user interfaces developed and database initiated with data.
Phase 5: Implementation and evaluation
The components built during development are now put into operational use. Any changeover
strategy can be used to put the developed system into work.
SYSTEM APPROACHES AND METHODS
1. STRUCTURED SYSTEM ANALYSIS
Structured methodology is an approach in which analysis and design and programming
activities are broken down into smaller easily managed parts.
The methodology helps prevent re-inventing the wheel i.e. it induces re-using some units of the
system as units of other systems thus increasing the volume of re-usable specification in
performing structured system analysis.
Different modeling techniques are used (these are methods used to illustrate organizational
object activities as associations). It may be graphical or textual.
Modeling techniques used
i. Data modeling – where diagrams and text entries are used to identify and provide facts
about business objects e.g. ELH, ERD
ii. Process modeling – involves the decomposition of business activities into functions,
categories of processes within functions and sub-categories of major process e.g. DFD
iii. Activity modeling – example is the system flowchart
iv. Procedure modeling – program flowchart ,HIPO (– Hierarchy Input Processing Output)
diagram, pseudocode and structured English
Object oriented modeling method – a relatively new technique which combines data modeling
and procedure modeling into one modeling methods
Structured System Analysis and Design Methodology (SSADM)
This is an integrated set of standards and guides for the analysts and design of a computer
system. It was developed to conquer the limitations of traditional system development
methodologies.
System development in earlier days was characterized by
Limited user involvement
Inadequate requirements elicitation
Use of ad hoc analysis and design techniques
Time consuming use of 3GL tools
Inflexible files and 3rd generation database management systems
SSADM adopts a prescriptive approach to information systems development in that it specifies
in advance the modules, stages and tasks which have to be carried out, the deliverables to be
produced and furthermore the techniques used to produce the deliverables
SSADM adopts waterfall approach model of system development where each phase has to be
completed and signed off before subsequent phases can begin.
In SSADM each stage is broken down into steps which are named and have unique numeric
identifiers and steps are further subdivided into tasks which are identified by numbers.
Benefits of SSADM
i. Enables developers to deliver system to user on time
ii. Enables developers or designers to deliver systems that meet user needs by continuously
involving users while modeling business activities and work practice
iii. Enables developers to deliver systems which responds to changes in business
environment
iv. Improve the effectiveness and economic use of the skills that are available
v. Improve quality by reducing error rates. Quality can be improved by detecting errors early
in the life cycle especially by involving users as well as skill practitioners in checking for
errors
Disadvantages of SSADM
i. A lot of time may be spent on investigation of the current system particularly where
there are a multiple of the current system
ii. Difficulties may be encountered in using design tools for communicating purposes.
2. SOFT SYSTEM METHODOLOGY
It is a way of dealing with problem situation on which there is no high socio-political and human
activity components.
It deals with soft problems which are difficult to define, have a large social and political
components.
1. . Problem situation
Involves finding out about the problem situation i.e who are the key players and how does the
process work.
2. Problem situation expressed in rich pictures
Refers to expressing the situation in all its richness through rich pictures (showing social,
political interaction between stakeholders).
3. Root definitions of relevant systems/naming relevant systems
Refers to root definitions because it is a stage out of which everything else grows. It moves out
of the real world into the systems world.
It involves selecting how to view the situation and producing different perspectives of looking at
a problem situation (root definitions)
4. Developing/building conceptual models
Involves developing conceptual models of what the system must do at each root.
5. Comparison of models and real world
The model developed is compared with reality, insights drawn from comparisons and ideas for
improvements determined.
6. Develop desirable and feasible interventions/changes
Possible interventions are explored. Identify feasible and desirable changes i.e.
7. Action to improve the situation
Recommendation for taking action to improve the problem situation are made and changes
implemented.
