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chaPter 7 • Using Data Flow Diagrams 205

diagram, partitioning it to facilitate programming. Each process is analyzed to determine whether it should
be a manual or automated procedure.
Six considerations for partitioning data flow diagrams are whether processes are performed by dif-
ferent user groups, whether processes execute at the same times, whether processes perform similar tasks,
whether batch processes can be combined for efficient processing, whether processes may be combined into
one program for consistency of data, and whether processes may be partitioned into different programs for
security reasons.

Keywords and Phrases

Ajax level 0 diagram
base element logical model
child diagram online process
context-level data flow diagram parent process
data flow diagram (DFD) partitioning
data flow diagram fragment physical data store
data store physical model
derived element primitive process
event modeling top-down approach
event response table transaction data store
event trigger transforming process
exploding Unified Modeling Language (UML)
external entity (source or destination) use case
functionally primitive vertical balancing
interface data flow

Review Questions

1. What is one of the main methods available for an analyst to use when analyzing data-oriented
systems?
2. What are the four advantages of using a data flow approach over narrative explanations of data
movement?
3. What are the four data items that can be symbolized on a data flow diagram?
4. What is a context-level data flow diagram? Contrast it to a level 0 DFD.
5. Define the top-down approach as it relates to drawing data flow diagrams.
6. Describe what “exploding” data flow diagrams means.
7. What are the trade-offs involved in deciding how far data streams should be exploded?
8. Why is labeling data flow diagrams so important? What can effective labels on data flow diagrams
accomplish for those who are unfamiliar with the system?
9. What is the difference between a logical data flow diagram and a physical data flow diagram?
10. List three reasons for creating a logical data flow diagram.
11. List five characteristics of a physical data flow diagram that a logical data flow diagram does not have.
12. When are transaction files required in a system’s design?
13. How can an event table be used to create a data flow diagram?
14. List the major sections of a use case.
15. How can a use case be used to create a data flow diagram?
16. What is partitioning, and how is it used?
17. How can an analyst determine when a user interface is required?
18. List three ways of determining partitioning in a data flow diagram.
19. List three ways to use completed data flow diagrams.

Problems

1. Up to this point, you seem to have had excellent rapport with Kevin Cahoon, the owner of a musical
instrument manufacturing company. When you showed him a set of data flow diagrams you drew, he
wasn’t able to see how the system you were proposing was described in the diagrams.
a. In a paragraph, write down in general terms how to explain a data flow diagram to a user. Be sure
to include a list of symbols and what they mean.