Hello world! I'm talking about data flow diagrams.

A Data Flow Diagram shows how data flows through the system.

I've opened draw.io.

And I'm going to create a new diagram.

Start with a blank diagram.

Create that.

And I'm going to go down here.

For symbols for data flow diagram.

And...

I'm going to start with.

an Entity

If we.

Double click on that.

I can type in there.

Customer

An entity here.

is an External entity.

They are.

People, places, offices, that interact with the system.

You can pick a color if you want you can make it rounded if you'd like.

And the next thing we're going to have is a process.

And.

[Make it bigger]

I'm going to double click on that.

And.

Process order.

And.

I need a data store.

Database.

And I'm going to have two databases here.

Move this over just a little bit.

And this one,

click on that,

Is going to be my customer

database.

And then I'm going to have another one.

Another one here

And the other one is going to be.

My product.

database

Now, The most important part.

is

Arrows.

so, Back up here.

Get an arrow.

I'm going to.

Attach pne end of it to the entity,

the customer.

I like all the lines to be nice and straight.

One of the nice things about this is that if we move.

The process.

That arrow moves with it.

And we have to give a name to this so let's double click on that.

And type.

Order

So,

The customer submits an order and we go in and we're going to process that order.

And...

We are going to

both

Send and receive.

Information.

From the customer database.

And we're also going to

put information.

into

Product database.

And again we're going to.

Click on that.

Order details.

And this one,

is going to be.

Update inventory.

This is all on a top-level.

If you think about it, processing nn order

We have to take their credit card information and send it to the bank and get that back whether it was accepted.

And we have to check the product database to make sure that we have the item in inventory that they are requesting.

We have to send some information back to the customer telling them I'm sorry that item is not in stock or thank you for your order with the order confirmation.

But there are some rules for this.

Every.

data flow

Has to go through a process.

So we have a customer sends an order that process that we process that order.

Update the customer database and we update the product database.

Every.

Process has to have at least one input and at least one output every database has to have both input and output.

And we usually keep the external entities around the outside and we keep the databases in the internal part Partly that's to keep lines from crossing.

We want this to look very neat and be easy to read.

If you think about.

This as just top-level we're not showing that.

Check if their credit card was accepted We're not showing those details but if we go down a level that we might show more of those details.

And when we're finished drawing this.

I'm going to.

Click.

Here to save

And I'm going to.

Ok, and I would put this

Somewhere where I can find it.

And store that for later. Let's go here to file,

And "save as", just make sure.

Order processor.

Download that.

Open save, just my downloads. So you can experiment with that. I could open one that I had done previously and edit it.

You need to play around with this a little bit.

So that you can create nice neat diagrams.

And that's it for now.