← ACARA Digital Technologies Years 7–8

Justifying keeping or removing a data item

A justification names the data item, the system's purpose and gives a because reason why the item is needed or could be removed. Test it by removing the item and checking the system still works.

Part of: ACARA Digital Technologies Years 7–8 — Digital Footprints and Data Minimisation — Module 22

Understanding Justifying keeping or removing a data item in ACARA Digital Technologies Years 7–8

What it does: This sentence names the item (home address), the purpose (delivering pizza) and gives a because reason. The same item is essential for one system's purpose and removable for another, so the purpose decides. A fix would be: 'Phone number is needed because the club must text parents if training is cancelled.'. After removing an item you must check the system still works. If it fails, the item is needed and the justification should say why.

Common mistakes: The data item must match the because reason. A parcel reaching the right door needs the home address, not a favourite colour. The line should be 'Item: home address'. A purpose says what the system is for. 'Collect more data' is not a real purpose and cannot justify keeping an item. It should name a real job, such as 'Purpose: send the class news'.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

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This module's key terms are also in a printable crossword (Modules 728–751) and word search (Modules 696–770).

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Each concept is reinforced from every angle — learned, then applied, then tested.

Learning
Duo
A school canteen app asks for each student's home address. Which is the better justification for REMOVING it?
Remove the home address because it feels private.The canteen app does not need the home address because orders are picked up at school, so it can be removed.
Matches
We collect phone numbers because we always have.
↓
The reason does not link to the system's purpose. 'We always have' is a habit, not a reason the item is needed.
Applying
Meanings
Term
The system needs this because
Meaning
A justification names the data item, the system's purpose and gives a because reason why the item is needed or could be removed. Test it by removing the item and checking the system still works.
Practice
Data item: mobile number
Testing
Gaps
The system needs this
Check Answer
Spots
1Item: favourite colour
2System: parcel delivery

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Quick Questions

1. A school canteen app asks for each student's home address. Which is the better justification for REMOVING it?
A. The canteen app does not need the home address because orders are picked up at school, so it can be removed. ✓
B. Remove the home address because it feels private.
A good justification names the data item, the system's purpose and gives a 'because' reason. The wrong answer gives no link to the purpose.
2. Which sentence starter shows a justification for KEEPING a data item?
A. Everyone else collects this so...
B. The system needs this because... ✓
'The system needs this because...' makes you link the data item to what the system does. 'Everyone else does it' is not a reason.
3. A library app records a student's email so it can send a reminder when a book is overdue. Which justification is complete?
A. The app needs the email because emails are useful.
B. The app needs the email because it sends overdue reminders, which is the purpose of the system. ✓
The complete justification names the item (email), the purpose (overdue reminders) and a because reason. 'Useful' is too vague.
4. You want to test whether a data item can be removed. What should you do?
A. Remove the item and check that the system still works. ✓
B. Keep the item in case someone wants it later.
If the system still does its job without the item, the item is probably not essential. 'Just in case' is not a justification.
5. A quiz app works fine after you delete the 'favourite colour' field. What does this tell you?
A. The field was not needed, so it can be removed. ✓
B. The field was essential, so it must be put back.
If the system still works after the item is removed, then the item was not essential for its purpose.

Match the Pairs

The system needs this because... → A sentence starter that begins a justification for keeping a data item by giving a reason linked to the system's purpose
Remove the item, then check the system still works → A test to decide if a data item is really needed: if the system still does its job without it, the item can be removed
A good justification names the data item, the system's purpose and a because reason → Home address is needed by the pizza app because it must deliver the order to the right door.
A data item can be essential for one purpose but not another → Birthday: needed to check age for a licence form, but not needed for a library book return.
We collect phone numbers because we always have. → The reason does not link to the system's purpose. 'We always have' is a habit, not a reason the item is needed.
Remove the email field. The sign-up form is now broken, but that is fine. → The student removed the item but ignored the test. If the system stops working, the item is probably essential and should be kept.

Key Term

The system needs this because
A justification names the data item, the system's purpose and gives a because reason why the item is needed or could be removed. Test it by removing the item and checking the system still works.

Fill in the Blanks

1. Item: email, Purpose: send receipts The system needs this because it sends the receipt to the buyer.
Hint: Type the linking word that starts the reason in a justification.
2. Item: home address Purpose: class quiz app Test: remove it, then check the app works.
Hint: Type the action you try on a data item to see if the system still works.
3. Item: home address Delivery: essential as parcels need it Quiz app: not needed, so remove it
Hint: Type the word that says this item is needed for the delivery purpose.
4. Data item: phone number Purpose: contact parents about trips Keep it because trips need a contact.
Hint: Type the label for what the system is meant to do with the data.
5. Test: removed email, login stopped working Result: keep it because login needs it
Hint: Type the decision you make when removing the item breaks the system.

Spot the Error

Question 1
A Item: favourite colour
B System: parcel delivery
C Needed because: the parcel
D must reach the right door
Line A — The data item must match the because reason. A parcel reaching the right door needs the home address, not a favourite colour. The line should be 'Item: home address'.
Question 2
A Item: parent email
B Purpose: collect more data
C The system needs this because
D it emails news to families.
Line B — A purpose says what the system is for. 'Collect more data' is not a real purpose and cannot justify keeping an item. It should name a real job, such as 'Purpose: send the class news'.
Question 3
A The system needs this anyway
B allergy info keeps students
C safe at the canteen.
Line A — A justification uses the sentence starter 'The system needs this because...' so that a reason follows. 'Anyway' gives no reason. The line should be 'The system needs this because'.
Question 4
A Item: school year level
B System: sports carnival app
C Needed because: I like it
D Remove it: sorting would fail
Line C — A because reason must link the item to the system's purpose. 'I like it' is a personal opinion, not a reason. It should say why the system needs it, such as 'Needed because: it sorts teams'.
Question 5
A System: swimming club sign-up
B Test: remove middle name: OK
C Verdict: keep it, it is needed
D Because it works without it
Line C — The removal test showed the sign-up still works without the middle name. The verdict must match the test, so it should be 'Verdict: remove it, not needed'.

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