CSE1IS Information Systems
Week 3 Lecture 1

Analysis, Design and Implementation of Information Systems - The SDLC

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:

• on time,
• within budget,
• satisfies the user's needs, and
• is considered as a success by a majority of stakeholders.
  
  

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.
• Project requests initiate from users (workers or managers) or management.
  • IT personnel (Systems Analyst) handle requests
  • Evaluate requests - compatibility with organisation's objectives, technical and economic feasibility.
    
    

The Systems Development Lifecycle (SDLC)

  is a framework (or methodology) for information system development.

It consists of  a set of  steps or phases. The terminology used may vary from text to text, but the ideas behind each step are essentially the same.

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.

Figure01-27 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 Figure01-28 (gif image - 254Kbytes)). This emphasises 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.

Note: according to Wikipedia's definition of SDLC there are 6 official phases:

1. Preliminary Investigation
2. Systems Analysis
3. Systems Design
4. Systems Development
5. Systems Implementation
6. Systems Maintenance

(Earlier versions of our text defined the SDLC as the first 5 of these 6 phases)

SDLC is a Waterfall analysis, design and development methodology.

Other design methodologies include prototyping, iterative, top-down and bottom-up.

Methodologies may incorporate Object-Oriented concepts from the design phase onwards.

SDLC Overview

1. Systems Planning

   (other commonly used names are Preliminary Investigation, Feasability Study)

   A preliminary investigation is normally initiated by some sort of system request.

   Objective:

   To identify the scope and nature of the problem

   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 or Feasibility Study for management.

2. Systems Analysis (Requirements Determination)

   Objectives:

   • 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

3. Systems Design

   Objective:

   • Design an IS that best  satisfies the user/managerial  requirements

   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 System Design Specification

4. Systems Implementation (Systems Development, Construction):

   Objective:

   • to convert the specification into a functioning system.

   Activities:

   • application programs are written, configured, tested and documented.
   • conduct system testing.
   • conversion of old data files
   • training users
   • operational documentation is written.
   • assessment or systems evaluation

   Result/Document:

   • a fully functional and documented system.

5. Systems Operation and Support (Systems Implementation and Maintenance):

   Objective:

   • to implement the new system i.e. put it into  production

   Activities:

   • completion of user documentation and training.
   • system changeover (text has this in stage 4).
   • evaluation of the system a regular intervals.

   Document/Deliverable:

   • a full functional/documented system in its operational environment

After the SDLC

During operation, an IS requires on-going maintenance.
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 a newinitiation 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!

CASE IN POINT 1.2: Global Hotels and Momma's (sic) Motels

(from page 25 of text)

Suppose you work in the IT department of Global Hotels, a multinational hotel chain. Global Hotels runs several specialized business support systems, including a guest reservations system that was developed in-house to meet the requirements of a large company with worldwide operations. Guests can make one-stop online reservations by visiting Global's Web site, which has links to all major travel industry sites.

Global Hotels just acquired Momma's (sic), a regional chain of 20 motels in western Canada . Momma's (sic) uses a vertical reservations package suitable for small- to medium-sized businesses, and a generic accounting and finance package. Should Momma's(sic) use Global Hotels' information systems or continue with its own? In your answer, consider issues such as business profiles, business processes, system interactivity, EDI, XML, e-commerce, and the characteristics of both information systems. What additional information would be helpful to you in making a recommendation?

Reference:

Shelly, Cashman & Rosenblatt, Systems Analysis and Design, 6th Edition, Course Technology, 2006.

Copyright © 2006 Brian Retallick

This page last updated by Monday 04 August 2008 by Chris Cope, La Trobe University, Bendigo