When decomposing a Level 0 DFD to Level 1, an analyst introduces a new…
2026
When decomposing a Level 0 DFD to Level 1, an analyst introduces a new external entity not present in the context diagram. This violates which principle ?
- A.
DFD balancing rule
- B.
Process decomposition rule
- C.
Data store naming convention
- D.
Functional cohesion rule
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Correct answer: A
The correct answer is Option A: DFD balancing rule. When decomposing a Level 0 Data Flow Diagram (DFD) into a Level 1 DFD, the principle of balancing must be maintained. This rule states that all inputs and outputs defined in a parent process (Level 0) must appear identically in the child processes (Level 1). Introducing a new external entity that was not present in the context diagram violates this rule because it changes the system's boundary and data flow relationships. The external entities represent sources or destinations of data outside the system; adding one implies new interactions that were not accounted for in the higher-level view. Option B is incorrect because process decomposition refers to breaking down a single process into sub-processes, not changing external entities. Option C is irrelevant as it concerns naming standards for data stores. Option D relates to software design principles regarding module functionality, not DFD structural integrity.