Data Flow Diagrams

What the ***** 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 data The 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 etc We are not concerned with what happens to the data before it reaches a source, or what happens to it after it goes past it!

Process The process BOX This is a process performed on the data e.g. search, produce a graph, perform calculation, create a mail merge letter, print 1 Search database Brief description of process Each process is numbered

Data Store The Open Rectangle D1Members file This is where data is stored e.g. members file, letters file etc Each store is numberedBrief description of store

Direction of Data Flow Arrows are used to show how symbols connect Details input into database Brief description of data used

Spend a little time creating the shapes and save them so that you can reuse them.

Level 0 / Context diagram This is an overview of the whole process Only has one process Does not show any data stores Customer Holiday booking system Book holiday 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 your system Make sure that you draw the key. Make sure you label each item.

Level 1 diagram This builds on the processes involved in here 1 Holiday booking system Customer Book holiday Receipt

Level 1 Diagram Customer 2 Holiday booked Payment made Receipt Bookings file D2 Holiday details Availability checked Customer Enquiry List of holidays 1 Customer records D1 Customer details Customer 3 Confirmation printed Printout of details Booking Information