Where does the data go?
A student reports a broken laptop on the help desk page. What happens to that report? Who sees it? Where is it kept?
A support team draws this as a picture. One look shows where the data comes from, what is done to it and where it ends up.
By the end of this lesson
Note
I can name each symbol in a data flow diagram and say what it stands for.
Key words
| Word | What it means | Example |
|---|---|---|
| Data flow diagram | a picture of how data moves through a system | DFD |
| Data source | a person or system that sends data in | |
| Data destination | a person or system that receives data out | |
| Process | a step that does something to the data | |
| Data store | a place where data is kept, such as a file or a list of records | |
| Label | words on an arrow that name the data |
The cells students fill in are left blank in this preview.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
What a data flow diagram is for
A data flow diagram, or DFD, shows how data moves through a system. It does not show how the data is stored in detail or how the code works.
Use one when you need to understand a system, explain it to a customer, or find where data could be lost or leaked. Draw it before you build or change anything.
The symbols and what they mean
| Symbol | Stands for | Example | Name it with |
|---|---|---|---|
| Oval | Data source or data destination | Student, technician | A noun |
| Rectangle with a small box top left and a title strip | A process, with its number in the small box | Check the fault | A verb and a noun |
| Open-ended rectangle: top and bottom lines, no right side, small box on the left | A data store, with its id in the small box | D1 Ticket list | A noun |
| Arrow | Data moving in one direction | From student to a process | A label on every arrow |
| Label | The name of the data on the arrow | Fault report | The data, not the action |
The cells students fill in are left blank in this preview.
Read it left to right
Note
The student is the source, drawn as an oval. The report goes into the process "Log the fault". A new ticket is saved in the Ticket list. "Assign to technician" reads open tickets and sends job details to the technician, the destination.