4.3.9 - SDLC - Systems Analysis

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  • Created by: Annie
  • Created on: 13-05-13 18:25
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  • Systems Analysis
  • What is it?
    • Systems Analysis
    • Follows the decision to create a new system on the basis of the Feasibility Report
      • The purpose is to detail the existing system and further understand the User Requirements
        • NOT the new system
    • Systems analysis is a detailed job often carried by specialist Systems Analysts
    • Poor systems analysis could mean mistakes from the old system are repeated in the new system
    • The outcome is a Systems Specification
  • Gathering Information
    • Interviews
      • With managers to reveal how the departments work and current problems
      • How they want  the new system to work and what information they want
      • Operational staff can supply fine detail on how the current system works
      • Very time consuming as a lot of people have got to be contacted
      • Need skilled interviewers to get the correct information out of people
    • Observation
      • Sit and watch how somebody does their job at present
        • To get a understanding of what they do, how, what information flows, the processes and any time delays, crashes and interruptions
      • Can be time consuming
    • Inspection of records
      • Studying paper based information
      • Can see what information is currently held and the way it is communicated between different departments, customers and the company
      • Can include charts, manuals, reports, minutes of meetings and documentation
    • Questionnaires
      • Ideal way to collection information as it is least time consuming
        • Economical to produce and distribute
        • Not everyone may fill them in though and response rates from posted surveys are usually low
      • People feel more involved, making the new system seem a positive thing
      • Cost involved in hiring people to ask and collect results
  • Tools and Techniques used for Systems Analysis
    • Data Flow Diagrams
      • To break the system down into
        • External sources of data
        • Processes of the system
        • External "sinks" of data
      • 3 Stages
        • 1. Context diagram to give an overview of the whole system with system shown as one process
        • 2.  Level 1 DFD: Breaking down the context diagram - typically has no more than 6 key processes
          • Can start to see Entity Relationships
        • 3. Level 2 DFD: This break down each process into further detail
        • External objects are ovals
        • Data flow are arrows
        • Processes are tables
    • Decision Tables
      • These can help understand the rules and actions of a system and also how a new system may behave
      • They detail the programming decisions that can be made by the computer
      • A table is used to structure the information
    • Systems Diagrams
      • Identify the data coming into the system (inputs)
      • What processes happen to the data?
      • What outputs are produced by the system?
    • Data Dictionaries
      • Typically a key feature of the design specification
      • The data dictionary needs details about the existing fields and how they are stored at this stage
      • Key information needed:
        • Entity Names
        • Relationships between entities
        • Attribute names and synonyms
        • Data type
        • Length
        • Validation to be used
        • Primary and foreign keys
    • Entity Relationship Diagrams
      • To show the relationships between tables
        • One to One
        • Many to Many
        • One to Many
        • Many to One

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