COMP 3513 – Quiz #1 SOLUTION SHEET

1.Consider the DFD in Figure 6–20 shown below. List three errors (rule violations) on this DFD.

Three major errors in Figure 6–20 are:

Process 1.0 (P2) has only inputs, making it a “black hole”. Data flow DF5 should not move directly from source E1 to data store

DS1 without first going through a process. Data flow DF1 should not move directly from source E1 to sink E2

without first going through a process. Other peculiarities (such as Process 1.0 has label P2 and the data

store has only a label, not a number) are only that, not errors. DF6 is an inappropriate line crossing; it makes for a more confusing

diagram and does not have to be drawn in this way.

2 .Consider the three DFDs in Figure 6–21 shown below. List three errors (rule violations) on these DFDs.These diagrams show the decomposition of process P1 on the level-0 diagram. Three particular logical errors in Figure 6–21 are:

The data store DS1, not DS2, should be represented on the level-1 diagram.

Data flow DF6 should not be on the level-1 diagram. Data flow DF3 should be an outflow on the level-1 diagram. Process P1.4.2 has no inputs and is thus a “miracle.”