What is a data flow diagram for?They look at data without considering the equipment needed.They are the first stage of designing a system.Show what data comes from and what data is needed
Source of dataThe OVAL = source of data (sink) This is a source of data e.g. order form from a customer Or an actual person…. The user, secretary, manager etcWe are not concerned with what happens to the data before itreaches a source, or what happens to it after it goes past it!
ProcessThe process BOX This is a process performed on the 1 data e.g. search, produce a graph, Search database perform calculation, create a mail merge letter, print Brief description of processEach process is numbered
Data StoreThe Open Rectangle This is where data is stored D1 Members file e.g. members file, letters file etc Each store is numbered Brief description of store
Direction of Data FlowArrows are used to show how symbols connect e ta bas a nto d np ut i ta ils i De Brief description of data used
Level 0 / Context diagramThis is an overview of the whole processOnly has one processDoes not show any data stores Book holiday Holiday Customer booking system Receipt
Task 1 – Create Level 0’s to show…How a secretary in a company produces a report.How a librarian produces a letter for overdue books.How a doctor produces a diet sheet for a patient.
Draw a Level 0 diagram for yoursystemMake sure that you draw the key.Make sure you label each item.
Level 1 diagramThis builds on the processes involved in here 1 Book holiday Holiday Customer booking system Receipt
Level 1 Diagram 1 Enquiry Customer details Availability D1 Customer recordsCustomer checked List of holidays 2 Payment made Holiday details Holiday D2 Bookings fileCustomer booked Receipt n rm atio Info k ing 3 Boo ConfirmationCustomer Printout of printed details