Unnormalised Form (UNF)
Context: FIT2094_MOC · the starting point of Normalisation · a form mapped directly to a relation · repeating groups in brackets, no PK
Quick Revision
- 🎯 Objective: map a client form directly to a relation before Normalisation ➔ raw starting point.
- 📦 Core Components: subject name ➔ all attributes ➔ repeating group in brackets.
- ⚡ Key Constraint: no PK yet; a UNF is not a valid relation; don’t flatten.
📝 Core
1. The UNF
- Definition ➔ the relation mapped directly from a form, before normalisation.
- Single named ➔ name by subject, not pluralised.
- No PK yet ➔ and repeating groups in brackets.
2. Building It
- Name by subject ➔ what the form represents.
- List all attributes ➔ faithfully.
- Bracket the repeating group ➔ attributes multivalued for one subject instance.
3. Rules
- Not a valid relation ➔ has a repeating group / non-atomic structure.
- No PK, no flattening ➔ don’t indicate a PK; don’t expand into tabular rows.
- No repeating group ➔ maps to a single relation through to 3NF.
When It Flips: an accurate UNF ensures the business rules survive into the normalised schema; errors here propagate. Multivalued attributes are the repeating groups (Attribute (Conceptual Modelling)); the bracketed group is what 1NF splits out.
📊 Exam Execution Trace
Manual Execution Trace
Building the UNF:
| Step / State | Action | Result |
|---|---|---|
| 0 (Init) | — | — |
| 1 | name by subject | PART |
| 2 | list attributes | part_no, …, part_sell |
| 3 | bracket repeating | (vendor_no, …, restock_payment) |
⚠️ Common Mistakes
- 💡 No PK, no flattening at UNF ➔ don’t indicate a primary key and don’t expand the repeating data into rows; brackets capture the repeating group 1NF will remove.
🧠 Active Recall
How do you represent a form as a UNF, and what must you not do?
- Hint: Subject + bracketed repeating group.
Answer
- Short answer: Name by subject, list all attributes, bracket the repeating group; don’t indicate a PK or flatten into rows.
- Why: As presented ➔ transcribe faithfully; design decisions come later.
Why is a UNF not a valid relation, and what if a form has no repeating group?
- Hint: Non-atomic + no key.
Answer
- Short answer: It has a repeating group and no PK, breaking the relation properties; a form with none maps to one relation.
- Why: 1NF adds only a PK ➔ no new relation when there is no repeating group.