How does data flow diagramming complement other IRD techniques?

1. Explain why data flow diagramming can be correctly thought of a process of “functional decomposition.”
2. State an accurate guideline for an analyst performing data flow diagramming on knowing when no additional levels diagramming are needed. In other words, what is an accurate “stopping rule”?
3. Explain the nature of the relationship between information requirements determination (IRD) and data flow diagramming.In other words, how does data flow diagramming complement other IRD techniques?

PS;

Plz write this 3 questions in 2-3 pages, plus 2-3 references.