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Applying the Three Rules

  1. Process 2.1 has no output. Process 2.2 has no input. It is usually easier to resolve a situation like this by first examining the process that has no inputs rather than the one with no outputs. The Reason? Well, it is easier to answer the question "What does the process need in order to produce its output?" rather than "What does the process do with its input?"
  1. So we will deal with Process 2.2 first. We can, in fact, go directly to Rule 3.
  1. Q What does Process 2.2 need in order to produce its output?

A It needs order.

Q Where will it get this from?

A 2.1.

Here is the updated diagram:

DFD after applying rules

Notice that we have also dealt with the problem of 2.1 having no output. This situation is quite common.

Next: Activity 7