Inference Rule (IR)
- Using the inference rule, we can derive additional FD (functional dependency) from the initial attribute set.
Types Of Inference Rule
The FD (Functional dependency) has 6 types of inference rule. Any rule can be used in-between two attributes
1. Reflexive Rule (IR1)
- In the reflexive rule, if B is a subset of A, then A determines B.
- Every attribute can determine itself also called Reflexive.
- If A ⊇ B then A → B
A ⊇ A , B → B , AB → B
2. Augmentation Rule (IR2)
- The augmentation rule is also called as a partial dependency.
- If A → B then AC → BC
3. Transitive Rule (IR3)
- In the transitive rule, if A determines B and B determine C, then A must also determine C.
- If A → B and B → C, then A → C
4. Union Rule (IR4)
- Union rule says, if A determines B and B determines C, then A must also determine B and C.
- If A → B and A → C then A → BC
5. Decomposition Rule (IR5)
- Decomposition rule is also called project rule. It is the reverse of union rule.
- If A → BC then A → B and A → C
6. Pseudo transitive Rule (IR6)
- According to Pseudo transitive Rule
- If A → B and BC → W then AC → W