Hello world.

This is Professor Joy.

I'm talking about the difference between

physical and logical models in systems analysis and Design.

The logical model tells you what.

And it is general.

The physical

tells you how, and it is very specific.

If I say call everyone and tell them the meeting is canceled.

You picture using a phone.

Instead, I could say notify everyone that the meeting is canceled.

If I put it that way,

I've removed the physical object, the phone, from my

description and you could brainstorm now and you

could think of different ways that you might notify

everyone that the meeting is canceled. So we're looking at the essence of this they need to be notified they don't

necessarily have to be called

on a telephone.

Another example: we could say the server gives the customer a menu.

Then we can picture a physical menu.

Instead, I could say, the customer reviews the menu.

And then I could brainstorm and I could say how would I

present this menu? Is it online? Could it be on a blackboard in

the restaurant or in the window of the restaurant?

Could it be on a device, or is it printed on paper?

Eventually we have to create a physical system and

actually implement it.

But we tried to put off the physical description of the

system until the very end when we're ready to

implement it and after we've had a chance to brainstorm

and think about different ways we might do that.