Current DFDs 1 Current Physical DFDs Produced while developing Requirements Catalogue and Current Environment Logical Data Structure Gather information by conventional analysis techniques (interviewing, observation, studying documents etc. ) Current Physical Data Flow Diagrams are usually built up by users and analysts jointly (during interviews, group sessions etc. ) Top-down approach useful for organizing large project teams Most ad hoc enquiries and reports should be documented in Requirements Catalogue and not on DFDs Starting points for DFDs may be (often a combination of) – Physical Document Flow Diagrams, – Physical Resources Flow Diagrams, – Context Diagram, or – the organisations structure

Current DFDs 2 Physical Document Flows Approach Step 1: List the Major Documents Step 2: List Sources and Recipients of data Step 3: Draw the Document Flows – Documents are represented as flows between sources and recipients – Each source or recipient is represented as an oval in the diagram Step 4: Agree the System Boundary Step 5: Identify Processes and Data Stores within the System

Current DFDs 3 Physical Document Flows Approach Sources, recipients, and document flows in Yorkies Drivers Local Driver Admin Local Booking Staff Local Office Reception Customers Head Office Vehicle Fleet Maintenance Local Depot Staff Agencies Booking Request Booking Request Booking Request Booking Sheet (Copy 1) Invoice Payment Customer List Booking Sheet (Copy 3) Booking Sheet (Copy 4) Booking Sheet (Copies 2,3,4) Driver Confirmation Driver Request Driver Request Driver Request Confirmation Driver Instructions New Vehicle Documents

Current DFDs 4 Physical Document Flows Approach System Boundary for Yorkies Drivers Local Driver Admin Local Booking Staff Local Office Reception Customers Head Office Vehicle Fleet Maintenance Local Depot Staff Agencies Booking Request Booking Request Booking Request Booking Sheet (Copy 1) Invoice Payment Customer List Booking Sheet (Copy 3) Booking Sheet (Copy 4) Booking Sheet (Copies 2,3,4) Driver Confirmation Driver Request Driver Request Driver Request Confirmation Driver Instructions New Vehicle Documents

Current DFDs 5 Physical Document Flows Approach Identify Processes and Data Stores Customers Local Office Reception Customers Local Booking Staff Booking Request Booking Request 1 Local Office Reception Booking Request Booking Request Receive Booking Request T2 (M) Booking Request 2Local Booking Staff Fill Out Booking Sheet Booking Sheet M1Booking Sheet File

Current DFDs 6 Physical Resource Flows Approach - an example for a part of Yorkies Vendor Buyer Customer Buy Vehicles Sell Vehicles Service Vehicles Receive Back Rented Vehicles Rent Out Vehicles Check Vehicles Returned Vehicles Vehicles Sold Vehicles OK VehiclesVehicles = Physical goods store Vehicles

Current DFDs 7 Physical Resource Flows Approach - include data flows Vendor Buyer Customer Buy Vehicles Sell Vehicles Service Vehicles Receive Back Rented Vehicles Rent Out Vehicles Check Vehicles Returned Vehicles Vehicles Sold Vehicles OK Vehicles Vehicles = Physical goods store Vehicles Vehicle DocumentsDocs Vehicle Docs Vehicle Documents Vehicle Docs Booking Sheet Copy 4

Current DFDs 8 Yorkies Level 0 or Context Diagram Fleet Maintenance YORKIES Bookings Invoicing Drivers Vehicles New Vehicle Documents Driver Availability Booking Sheet Booking Request Customer Drivers / Agencies Vehicle out of service Instructions Invoice Payment Payroll Driver Hours Agency Days

Current DFDs 9 Use to define the processes Easiest approach for complex systems Dependent on the organisations structure = functional structure Main function of the Local Office Booking staff is to fill the bookings 'Fill Booking Sheet' will become a top-level Process on the Data Flow Diagram. Organisations Structure

Current DFDs 10 Managing Director Local Office Admin Marketing & Financial Directors Head Office Bookings Local Office s Marketing & Pricing Accounts Receivable Accounts Payable General Ledger & Budgeting Invoicing Customer Records Payroll Running Costs Vehicle Fleet Management Maintenance Sales & Purchases Local Office Manager ReceptionBooking Driver Admin Depot Staff Organisations Structure Organisation chart for Yorkies Ltd.

Current DFDs 11 All approaches should lead to a top level DFD similar to this: 6HO Accounts Invoice and Maintain Customer Records 3Depot Staff Record Vehicle Departure and Return 5HO / Local Admin Administer Local Unfilled Bookings 4Local Driver Admin Find and Notify Drivers 2Local Booking Fill Booking Sheet 1Local Reception Receive Booking Request * a Customer e Payroll b Driver Agency c Drivers d Fleet Maintenance a Customer T1(M)Booking Request M2Driver Instructions M1Booking Sheets Booking Request Booking Request Booking Sheet Copy 1 Driver Instructions Driver Instructions Driver Request Booking Sheet Copies 2-4 Driver Hours Driver Name Driver Hours and Mileage Vehicle Info (Out of Service) Booking Request Booking Requests Batch of Confirmed Bookings Unable to fill Bookings Booking Sheet Copy 4 Invoice Payment Booking Sheet Copy 2 Complete New Vehicle Documents Vehicle Out of Service Driver Availability Driver Hours Agency Days Driver Instructions Customer Lists

Current DFDs 12 Decomposition to lower levels Expand process boxes to level 2, and possibly to levels 3 and 4 Decompose if: – there are more than eight data flows in to or out of the process – the process name is complex or very general e.g.. Record Customer Information, Send Invoice and Receive Payment or Maintain Customer Information. At the bottom level, each process should have: – a brief specific name – between two and eight data flows

Current DFDs 13 Level 2 Data Flow Diagram of process 4 for Yorkies Below bottom level use Elementary Process Descriptions (narrative, formulae, decision tables) 4.2Driver Admin Notify Driver 4.1Driver Admin Find Driver 2Local Booking Fill Booking Sheet 4.3Driver Admin Find Agency Driver 4.4Driver Admin Record Driver/ Agency Time Driver Agency Payroll M1Booking Sheet M4/1Driver/Agency Register Driver Request Driver Availability Driver Instructions Driver Name Driver Details No Driver Time Driver Hours Agency Days Driver/ Agency Time Suitable Driver Agency Names Driver Availability Driver Instructions Driver Instructions 4FIND AND NOTIFY DRIVERS * * * * M2Driver Instructions