Analysis

• Analysis


  The investigating of a problem within a system
• Purpose of the analysis stage


  • To establish user requirements
  • To allow the systems analyst to understand the organisation in terms of input and output
• Constraints involved in the analysis stage

  • Time
  • Scale
  • Existing HW and SW capability
  • Fact Finding needs to be carried out to identify user requirements
• Describe Advantage Disadvantage (DAD)


  A technique to evaluate
• Interviews


  • Users are asked questions on a one-to-one / group level about strengths and weaknesses of the current system
  • Staff can answer in detail
• Questionnaires


  • Users complete a set of pre-defined questions containing open/closed questions
  • Questions are answered anonymously so users can answer honestly
• Observation


  • Analyst shadows a user carrying out a process to see first-hand what their role entails
  • Analyst can get an idea of the volume of data being processed
  • Analyst can see how data flows through an organisation
• Document sampling


  • Analyst can find out how data is input, collated, processed and reported by looking at typical documents like invoices/receipts
• Functional requirements


  Specify what a system must do
• Non-functional requirements


  Specify additional criteria that the system is judged on
• Functional requirements


  • RFID technology must be used to record stock movement
  • Stock breakages will be entered manually
• Non-functional requirements


  • Queries will be completed in an agreed time
  • Backups prepared in hourly intervals
• Functional requirements


  • Allow users to request to reserve an item
  • A reservation request should be automatically generated
• Non-functional requirements


  • When an item is reserved online or in-store, it is recorded to the DB within 1 second and removed from the shop floor in 60s
• Functional requirements


  • Calculate gross pay, calculate and deduct tax, and print wage slips
• Non-functional requirements


  • Calculating additional payments e.g. overtime
• Functional requirements


  • Calculating a total bill and adding VAT or a delivery charge, also printing receipts
• Non-functional requirements


  • Adding items billed to a receipt in 1 second
• Data flow diagrams (DFDs)


  Provide a visualisation of a system at different levels, illustrating how the system interacts with external entities, processes, data flows and data stores
• Context diagram (Level 0 DFD)


  Sees the system as one main process, only identifies the main data source and how data flows in and out, does not consider data stores
• Level 1 DFD


  Breaks main processes into a number of sub-processes, shows how data flows between the sub-processes, indicates data stores and how data is stored