Introduction
This topic is covered in your textbook, Shelly, Cashman & Rosenblatt, on pages 20-24. The terms used differ from text to text so I will use those found in your text but also give the more generic terms.
The following ideas apply to all large systems - anything that displays structure and order eg. Space shuttle, Westgate Bridge, Windows XP, Police Department criminal records database.
Remember that the aim in developing an IS should be to produce an IS that is:
Why would we wish to analyse/design/implement an information
system?
We may need to build an information system from 'scratch'.
An existing information system may need to adapt to a changing environment.
An existing information system may no longer meet the information requirements of an organisation.
An existing manual information system may need to be computerised.
An existing information system may have 'problems'.
New technology may provide new opportunities for the business.
Each phase of the SDLC uses the results of the previous one. In other words there is some sequence to the steps involved.
The SDLC is document driven. This means that at crucial stages during the process documentation is produced. A phase of the SDLC is not complete until the appropriate documentation or artifact is produced. These are sometimes referred to as deliverables. A deliverable may be a substantial written document, a software artifact, a system test plan or even a physical object such as a new piece of technology that has been ordered and delivered. This feature of the SDLC is critical to the successful managment of an IS project.
Figure 1-27 of the text provides a diagrammatic overview of the SDLC and some major deliverables.
The SDLC can also be viewed from a more process
oriented perspective (see Figure 1-28). This emphasizes the parallel nature of some of
the activities and presents activities such as system maintenance as an
alternative to a complete re-design of an existing system. Hopefully the
notation used to express this view will become clearer after you have worked
through the material on data flow analysis
A preliminary investigation is normally initiated by some sort of system request.
Activities include:
Problem identification.
A preliminary look at the problem area.
Evaluation of the feasibility of possible courses of action.
Some sort of
recommendation for future action.
(including alternatives
and the feasibility of each)
Document/deliverable: A preliminary investigation report/ feasibility study for management.
2. Systems Analysis (Requirements Determination)
Objective: To develop a detailed understanding of the current system.
To identify the areas that need modification to solve the problem.
To determine user/managerial requirements.
Activities include:
data gathering (fact finding) activities such as
interviewing
research/document collection
questionnaires
observation
modelling activities such as
developing models to document your understanding (data flow diagrams, E-R diagrams)
documentation activities
interview, questionnaires reports etc
development of a system(data) dictionary to document the modelling activities
Document/Deliverable:
A systems requirements report
Activities:
design all components of the system
procedures(manual/automated)
application software
input/output/user interface
files/database
internal/external controls
Document/Deliverable:
a `blueprint' or a design specification
activities:
application programs are written, tested and documented.
conduct system testing.
operational documentation is written.
result/document:
a fully functional and documented system.
activities: conversion of data to the new system files.
training of end users.
completion of user documentation.
system changeover.
evaluation of the system a regular intervals.
Document/Deliverable:
a full functional/documented system in its operational environment
Some minor modifications may be required
*
to correct errors (maintenance)
*
add further functionality to the system (enhancements)
Note:
A requirement for substantial maintenance or enhancement may result
in the initiation of the SDLC. Hence the term systems development life
cycle. In other words all Information Systems have a finite life. There
comes a time when they no longer meet the current requirements and remedial
action has to be taken!