Data flow diagram (DFD)

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Definition

A diagram that shows how data moves through a system between processes, data stores and external entities.

Example: Voting system: voter, vote data, count.

Found in: syllabus, course specifications, school notes, past SDD papers.

Short version to memorise (key terms bank)

Data flow diagram.

Where you'll use it in the test

Syllabus area: Diagrams and tools.

Question types it can appear in

Drawing: Draw or complete a DFD
Short answer: Define, outline or explain it and tie it to the scenario.
Multiple choice: Pick the option that matches the definition or example.

Where it has appeared in the paper

The Software Engineering Project (Part D). Part letters follow each paper’s own layout.

How to use it

A model sentence

General advice, built from the definition and example above

Diagram: “A diagram that shows how data moves through a system between processes, data stores and external entities.” Then apply it: Voting system: voter, vote data, count.

In a short answer, give the definition in your own words first, then tie it to the situation in the question. Do not copy the example above unless it fits the scenario.

Command words used with it

From the linked past questions

Explain: Relate cause and effect; make the relationship between things evident; provide why and/or how. (2024 Software Design and Development HSC Q25 (4 marks): Documentation)

Go deeper

Flashcard: Data flow diagram (DFD) in Diagrams and Modelling Tools (Years 11 and 12) · study that set
Memorise: Drawing rules: DFD, structure chart, storyboard, decision tree, class diagram, ERD
Key terms bank entry: DFD
Master answer: sdd2024-q24 (10 marks, extended) (Master model answers: The Software Engineering Project (written answers))
Notes: Modelling tools: DFD, structure charts, storyboards, flowcharts, class diagrams (The Software Engineering Project (Year 12))
Notes: Drawing rules: DFD, structure chart, storyboard, decision tree, class diagram, ERD (Pseudocode, flowcharts and diagram rules)
Full term page: every question, note and marking comment for Data flow diagram (DFD)

Check yourself

Describe or sketch “Data flow diagram (DFD)”: what it shows, its parts and when you would use it.

Reveal the answer

A diagram that shows how data moves through a system between processes, data stores and external entities.

Example: Voting system: voter, vote data, count.

Could be tested as: Drawing, Short answer, Multiple choice.

Quick multiple choice

In a data flow diagram (DFD), a data store is shown to:

Show a loop
Show a decision
Represent a person outside the system
Hold data that persists between processes, such as a file or database table

Show the answer

DFD elements: external entities (sources/sinks), processes, data stores and data flows. Data cannot flow directly between two data stores or two entities.

Source: original (written for this study pack; not a NESA question). Open it in the multiple-choice bank.