Information Systems 2nd edition A Business Approach

1
Information Systems 2nd editionA Business
Approach

• Systems Development

2
The IS Development Context

• Systems development methods are abstraction
  techniques that aim to simplify the complexity of
  the real world
• These methods are used by information systems
  (IS) professionals to model the data and the
  processes in organisations
• Instead of using ad hoc methods a more formal
  process, or methodology, is typically used for IS
  development

3
The Systems Development Life-Cycle

• The systems development life-cycle (SDLC) is a
  structured framework for developing information
  systems.
• It breaks down the development process into
  various phases and provides a project management
  context to work within.
• The main phases are
• analysis, design, implementation and maintenance

4
Dangers of an Ad Hoc Approach

• The completed system is not what the users want
• The customers do not use the system
• There is much conflict in the development of the
  system
• Resources are wasted
• People may have to work harder than needed
• The system does not produce the right information
• The system is not finished on time
• The developers get a bad reputation

5
Problems with the SDLC

• The steps involved are large easy to lose sight
  of what is happening
• User requirements are continually evolving easy
  to deliver the wrong system
• Can cause too much commitment to planning
  ignoring the realities!

6
The Skills Required by Systems Analysts

• Interpersonal skills
• Communication skills
• Presentation skills
• Analytical and problem solving skills
• Business knowledge
• Technical skills

7
Expanded SDLC
8
IS Planning

• IS plans are a method of strategically
  positioning the organisation in its use of
  information technology
• The plan includes
• broad directions for the technology platform
• the network infrastructure
• the software architecture
• the key data and processes of the business
• identifying the IS/IT expertise and skills
  required by the organisation
• Helps assess the relevance of potential projects

9
Feasibility Phase

• The feasibility phase involves gathering
  information on, and understanding, the current
  system if there is one
• Problems are identified and the benefits of
  solving them are assessed
• If no current system exists then research maybe
  carried out on similar systems in other
  organisations
• It is a preliminary investigation to identify the
  scope of the project and determine the projects
  validity

10
Feasibility Phase

• A decision must be made whether to
• move on to the next stage of the life-cycle
• to cancel the project altogether
• to shelve the project for the time being until
  conditions become more favourable

11
Analysis Phase

• A systems development project usually involves an
  examination of the current operations and systems
• The problems associated with any information
  system fall into broad categories
• The costs associated with the problems can then
  be estimated
• If the proposed system is completely new, then
  this phase can be used to research systems in
  other organisations

12
Requirements Phase

• After studying the current system the analysts
  must attempt to define the requirements for the
  proposed system
• This phase requires end-user involvement and uses
  a range of information gathering techniques
• The emphasis is on defining what is information
  is required not how the system should be
  physically implemented

13
Information Gathering

• Analysing company documentation.
• Analysing forms, files and database records.
• Questionnaires.
• Interviews.
• Informal conversations with users. Joint
  Application Design (JAD).

• Visits to other organisations.
• Research topics in magazines and journals.
• Observation of the systems in action.

14
Advantages of CASE

• Improves the quality of system documentation
  (i.e. better presentation, fewer errors and
  omissions)
• Improves the quality of the completed system
• Improves communication between analysts
• Improves maintainability of system
• Can potentially speed up the development process

15
Alternative Solutions Phase

• The alternative solutions phase involves
  identifying possible implementation solutions for
  the requirements.
• Ideally, several options are proposed rather than
  one.
• The analyst presents these to management and they
  can make a decision regarding which to choose.
• The reasons for choosing a solution are business
  reasons

16
Design Phase

• Systems design is a physical stage of the systems
  development life-cycle
• It concentrates on how the proposed system will
  be designed
• All aspects of the proposed systems have to be
  designed

17
Design Activities
18
Implementation Tasks

• Rooms and buildings altered
• Database set up
• Data keyed into database
• Programs coded
• Programs tested and system tested
• Security measures put in place
• Security measures tested

• Training of staff
• Documentation updated
• Hardware installed
• Systems software set up
• Applications software installed
• Network installed
• System hand-over
• Reviews of the system

19
System Conversion

• Systems conversion is a stage to change from one
  system to another.
• There are a number of methods
• 1. Direct conversion on a set date
  dispense with old system and start with new
  system.
• 2. Parallel conversion run both systems for a
  time.
• 3. Pilot conversion the system is tested
  in one location before others are converted.
• 4. Phased conversion sub systems
  are implemented one at a time.
• 5. Evolutionary conversion this takes
  a perspective that a system evolves in
  small increments

20
Maintenance

• Maintenance projects can be divided into two
  categories
• The first category is related to correcting
  errors in the system
• The errors may have been detected during the
  systems development process but were left to a
  later date for correction
• Changes will need to be made to the system at
  various times due to changing requirement

21
Systems Development Methodologies

• An IS methodology can vary from a series of steps
  used in solving a problem, to a general approach
  to problem solving
• One or more methodologies can be used in the same
  project
• A definition of the term methodology is
• A collection of philosophies, phases, procedures,
  rules, techniques, tools, documentation,
  management and training for developers of
  information systems.

22
Questions Addressed by a Methodology

• How a project is to be broken down into stages?
• What tasks are to be carried out at each stage?
• What outputs are to be produced?
• When actions or events are to be carried out?
• What constraints are to be applied?
• What support tools are to be utilised?

23
Systems Modelling

• The two most commonly used types of modeling in
  systems development are
• data modeling (Entity Relationship Diagrams)
• process modeling (Data Flow Diagrams)
• There are a number of systems development
  methodologies which employ both modeling
  approaches.
• Entity Relationship Diagrams represent a static
  view of the data in a system
• Data Flow Diagrams are used to model the dynamic
  aspects of the systems or how the data are
  changed (processes)

24
Data Flow Diagram
25
Entity Relationship Diagram
26
Example IS Methodologies

• Information Engineering
• Object Oriented Methodology
• Prototyping
• Rapid Application Development (RAD)
• Soft Systems Methodology (SSM)

27
Summary

• Systems development starts with an understanding
  of the business
• you need to speak the same language as the client
• Human factors are important
• good communication and client involvement improve
  the chances of success
• Systems developers use a range of methodologies
  and techniques

28
(No Transcript)