COMP9311 Assignment 2 Solved

Assignment 2
Please make sure that you always use notations consistent with lecture notes. Different notations will not be accepted. The deadline for assignment 2 is: 


Question 1 (8 marks) 
Consider a relation 𝑅(𝐴, 𝐵, 𝐶, 𝐷, 𝐸, 𝐺, 𝐻, 𝐼, 𝐽) and its FD set 𝐹 = {𝐴𝐵 → 𝐶𝐸, 𝐷 → 𝐺𝐻, 𝐸 → 𝐵𝐶𝐷, 𝐶 → 𝐷𝐼, 𝐻 → 𝐺, 𝐸𝐻 → 𝐼}. 

1)     Check if 𝐶 → 𝐽 ∈  F+. (1 mark) 

2)     List all the candidate keys for 𝑅. (2 marks) 

3)     Find a minimal cover 𝐹𝑚 for 𝐹. (2 marks) 

4)     Decompose into a set of 3NF relations if it is not in 3NF. Make sure your decomposition is dependency-preserving and lossless-join. Justify your answers. (3 marks) 

Question 2 (12 marks)
Consider a relation 𝑅(𝐴, 𝐵, 𝐶, 𝐷, 𝐸, 𝐺, 𝐻, 𝐼, 𝐽) and its FD set 𝐹 = {𝐴𝐵 → 𝐶𝐸, 𝐷 → 𝐺𝐻, 𝐸 → 𝐵𝐶𝐷, 𝐶 → 𝐷𝐼, 𝐻 → 𝐺, 𝐸𝐻 → 𝐼}. 

1)     How many super keys can be found for R? Compute the total number of super keys and list 5 of them. (2 marks) 

2)     Determine the highest normal form of 𝑅 with respect to 𝐹. Justify your answer. (2 marks) 

3)     Regarding F, is the decomposition R1 = {𝐴𝐵𝐶𝐷𝐸}, R2 = {𝐸𝐺𝐻}, R3 = {𝐸𝐼𝐽} of 𝑅 dependency-preserving? Please justify your answer. (2 marks) 

4)     Regarding F, is the decomposition R1 = {𝐴𝐵𝐶𝐷𝐸}, R2 = {𝐸𝐺𝐻}, R3 = {𝐸𝐼𝐽} of 𝑅 lossless-join? Please justify your answer. (3 marks) 

5)     Decompose it into a collection of BCNF relations if it is not in BCNF. Make sure your decomposition is lossless-join and briefly justify your answers. (3 marks) 

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