Question

What is the difference, if any, between a context diagram and a level 0 diagram?

Answer 1

There are some conflicts in the literature about these two terms.
Refer page 54 of this book for example. It is highly rated on google books and is a standard text in many schools. It says that a context diagram is the same as a Level 0 DFD. This one disagrees on page 210.

I’ll first address the notion of “levels”.

As we know, initially, the whole of the system is represented by one big block, and interactions with the system are clearly depicted. Initially, we are seeing the system with a naked eye.

Now, think of yourself holding something like a microscope. You place the lens above the system block and zoom in. This “zooming in” takes you to the next level in the hierarchy. So now, you see that the system is made up of a number of blocks.

You pick up any of the sub-blocks, and then zoom in again, thus going to the next level and so on.

So we see that there is a hierarchy of diagrams, with each level taking us to the next level of detail. The only bone of contention that now remains is name of the first level (The view with the naked eye).

As you can see, the question is not very objective, hence the ambiguity.

We can have :

Context Diagram -> 
                  Level 0 DFD ->
                                    -> Level n DFD</pre>

OR

Context Diagram/Level 0 DFD 
                              ->Level 1 DFD
                                              ->Level n DFD

It boils down to which one looks better. In my personal opinion , the first hierarchy is more apt. This is because initially, all we see is the system and the context within which it operates. I feel that anyone who understands the explanation should’t worry much about the nomenclature.

Refer this for more.