Follow these steps in order to draw DFDs

  1. Read and re-read the narrative that describes the process you wish to diagram.

  2. Identify the nouns which describe objects that interact with the system.

  3. Identify verbs that describe the actvities performed by the objects.

  4. Match the nouns and verbs. Identify nouns that do not perform any information processing activities for the system under study.
    1. Generally, non information processing activities relate to sending and receiving data. These are the external entities.
    2. In contrast, information processing activities relate to entering, filing, preparing, classifying, sorting, verifying, etc.....

  5. Draw the context diagram using 1 circle and squares for the external entities. Draw the data flow lines. Label the process and data flows.

  6. Draw the level 0 diagram.
    1. Group like activities related to information processing. Determine suitable name describing the process.
    2. Draw bubbles for each level 0 process. Include the external entities and their data flows. Connect level 0 processes with data flow lines. Label new data flow lines.
    3. Include data files if needed to accurately describe processing.
    4. Verify that the level 0 diagram balances with the context diagram.

  7. Contine to explode and refine the diagram.

Here is an example based on the text's review problem, p. 58.