Where does the survey answer go?
A pupil submits a survey answer on a web page. What happens next? Is it checked? Where is it kept? Who reads it?
A data analyst draws the answer's whole journey on one page. That drawing finds the places where data could be lost or wrong.
Key words
| Word | What it means |
|---|---|
| Data flow diagram | a picture of how data moves through a system, called a DFD |
| Data source | a person or system outside the system that sends data in |
| Data destination | a person or system outside the 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 table of records |
| Arrow | data moving in one direction |
| Label | words on an arrow that name the data |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can say what a DFD is for and name each of its symbols: sources, destinations, processes, data stores, arrows and labels.
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 DFD is for
A data flow diagram shows how data moves through a system. It shows where data comes from, what is done to it, where it is kept and where it goes.
It does not show who owns what, or the order of steps like a recipe. Use it before you build or change a system, to explain it, or to find where data could go wrong.
The symbols and what they mean
| Symbol | Stands for | Example | Name it with |
|---|---|---|---|
| Oval | A data source or a data destination | Pupil, head of year | A noun |
| Rectangle with a small box top left and a title strip | A process, with its number in the small box | 1 Check the answer | A verb and a noun |
| Open-ended rectangle with a small box on the left | A data store, with its id in the small box | D1 Survey answers | A noun |
| Arrow | Data moving in one direction | From a pupil to a process | A label on every arrow |
| Label | The name of the data on the arrow | Survey answer | The data, not the action |
The cells students fill in are left blank in this preview.
Drawing the exam shapes on paper
Important
The drawing tool makes an oval, a plain rectangle and a cylinder. On paper, draw each process with a small id box top left and a title strip. Draw each store as an open-ended rectangle with a small id box on its left.