Thinking in layers

This lesson’s goals

Web tech is messy. Learn a way of thinking that makes it easier to understand.

The problem

Web tech is complex. Lots of pieces, all connected together.

Don’t try to understand it all at once. You’ll just get confused. Everyone does.

You need a way to break the Web up into chunks. Then you can understand each chunk by itself.

Just as there are different ways to slice cheese (drool!), there are different ways to slice up the Web. This lesson shows one way to slice up the Web to make it easier to understand.

Alison and the light layers

Here’s Alison.


Here’s Alison dancing to the light of her favorite lamp.

Alison dancing

Alison doesn’t pay much attention to the lamp. If she needs light, she turns it on. If not, she leaves it off.

Alison knows how the lamp works. She knows about bulbs, electricity, switches, and stuff. But normally she doesn’t think about all that detail. Too dark? Turn the lamp on. That’s all she needs to do.

Only when the lamp doesn’t work does Alison need to think more. Suppose she paws the switch and nothing happens. She remembers what she knows about lamps, and first checks to make sure the lamp is plugged in. It is. OK, how about the bulb? Aha! It’s burned out. Get a new one, put it in, turn on, and dance, baby, dance!

Alison thinks about the lamp in layers. She normally thinks at the on/off layer:

Lamp layers

The on-off layer is simple. The lamp is on, or it’s off. That’s it. Thinking at this layer doesn’t take much time, or much learning. And it’s useful. When Alison has the goal “get light,” the on-off layer is all she needs to think about.

But if the lamp doesn’t work, then Alison thinks about the lower layer. Bulbs, plugs, and stuff. Things she can usually ignore.

We think in layers all the time. Cars, stereos, even our bodies. Life is easier when you can ignore details. Our brains would get clogged if we had to keep all of the details in mind all of the time. So we normally think at the higher layers, ignoring the details that make those layers work.

Web layers

The Web is like that, too. It’s best to ignore the details most of the time. But if you want to create and maintain Web sites, you need to understand what’s going on under the hood. Just a little bit.

We’ll talk about the Web in three layers:


The top layer actually shows the pages. That’s the layer most people work in most of the time.

The middle layer is about how computers send information to each other. The bottom layer is all the geeky electronics and stuff.


Is there really a layer called “bucket o’ numbers?”


The layers are just ways of thinking about what is going on. I made up this three-layer stack for CoreDogs.

Other writers use different stacks, depending on how detailed they want to get. Talk to a geek, and you might hear about seven layers. But CoreDogs covers only the most important stuff. Three layers is enough for that.


The Web is complex. Lots of pieces.

It’s easier to think about it in layers. When you think about one layer, you can ignore the others.

The Web has three layers: display, service, and bucket o’ numbers.

What now?

Let’s talk about the lowest layer.