Figure TB-4

Essay

Figure TB-4.5 shows a level 0 logical data flow diagram for a billing system. Also shown for reference is the context diagram for the system. The logical data flow diagram intentionally violates several of the guidelines and other techniques presented in the text for drawing data flow diagrams.
Required:
Identify as many of the errors in the logical data flow diagram construction as you can. In the logical data flow diagram, place consecutive numbers (each in a circle) next to the points at which the errors exist. On your solution sheet, list the numbers and write a one- to two-sentence description of each error and what the corrected diagram should depict. If an error occurs in more than one place, mark each occurrence of the error. Error 1 is provided as an example of how to construct the solution. Do not identify nor correct any errors that may exist on the context diagram.
\begin{array}{c}\begin{array}{lll}\underline{Error }\\1\\\\\\\\\\\\\\end{array}\begin{array}{lll}\underline{Error Description}\\\text{The flow from bubble 2.1 to the Accounts receivable department is not labeled. The}\\ \text{flow on the context diagram indicates that copy 3 of the sales invoice is sent to the}\\ \text{accounts receivable department.}\\\text{Correction: Add a label to the flow from bubble 2.1 to the Accounts receivable}\\\text{department. But, because data flows on a logical data flow diagram (DFD) should}\\\text{describe the nature of the data not how the data are transmitted, we should label this}\\\text{flow "Record sales invoice"}\end{array}\end{array}