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As you know there are three Armostrong's Axioms for inferring all the functional dependencies on a relational database. (X, Y and Z are set of attributes)

1. Reflexivity: If X ⊆ Y, then Y → X
2. Augmentation: If X → Y, then XZ → YZ for any Z
3. Transitivity: if X → Y and Y → Z, then X → Z

I understand the augmentation and transitivity for example if we had such schema:

SOME_SCHEMA(a, b, c, d)

with such functional dependencies:

1. a → b
2. b → c

By using augmentation we could get ac → bc or by using transitivity we could get a → c and much more, however I am not sure how to infer more functional dependencies using reflexivity axiom? What does it really mean that some attribute is a subset of some other attribute?

Could you show me an example using my schema or creating your own, please?

Thank you in advance!

P.S. Not sure what tag I should use for this question, feel free to change it and remove this line.

As you know there are three Armstrong's Axioms for inferring all the functional dependencies on a relational database. (X, Y and Z are set of attributes)

1. Reflexivity: If X ⊆ Y, then Y → X
2. Augmentation: If X → Y, then XZ → YZ for any Z
3. Transitivity: if X → Y and Y → Z, then X → Z

I understand the augmentation and transitivity for example if we had such schema:

SOME_SCHEMA(a, b, c, d)

with such functional dependencies:

1. a → b
2. b → c

By using augmentation we could get ac → bc or by using transitivity we could get a → c and much more, however I am not sure how to infer more functional dependencies using reflexivity axiom? What does it really mean that some attribute is a subset of some other attribute?

Could you show me an example using my schema or creating your own, please?

Thank you in advance!

P.S. Not sure what tag I should use for this question, feel free to change it and remove this line.

As you know there are three Armostrong's Axioms for inferring all the functional dependencies on a relational database. (X, Y and Z are set of attributes)

1. Reflexivity: If X ⊆ Y, then Y → X
2. Augmentation: If X → Y, then XZ → YZ for any Z
3. Transitivity: if X → Y and Y → Z, then X → Z

I understand the augmentation and transitivity for example if we had such schema:

SOME_SCHEMA(a, b, c, d)

with such functional dependencies:

1. a → b
2. b → c

By using augmentation we could get ac → bc or by using transitivity we could get a → c and much more, however I am not sure how to infer more functional dependencies using reflexivity axiom? What does it really means that some attribute is a subset of some other attribute?

Could you show me an example using my schema or creating your own, please?

Thank you in advance!

P.S. Not sure what tag I should use for this question, feel free to change it and remove this line.

As you know there are three Armostrong's Axioms for inferring all the functional dependencies on a relational database. (X, Y and Z are set of attributes)

1. Reflexivity: If X ⊆ Y, then Y → X
2. Augmentation: If X → Y, then XZ → YZ for any Z
3. Transitivity: if X → Y and Y → Z, then X → Z

I understand the augmentation and transitivity for example if we had such schema:

SOME_SCHEMA(a, b, c, d)

with such functional dependencies:

1. a → b
2. b → c

By using augmentation we could get ac → bc or by using transitivity we could get a → c and much more, however I am not sure how to infer more functional dependencies using reflexivity axiom? What does it really mean that some attribute is a subset of some other attribute?

Could you show me an example using my schema or creating your own, please?

Thank you in advance!

P.S. Not sure what tag I should use for this question, feel free to change it and remove this line.

As you know there are three Armostrong's Axioms for inferring all the functional dependencies on a relational database. (X, Y and Z are set of attributes)

1. Reflexivity: If X ⊆ Y, then Y → X
2. Augmentation: If X → Y, then XZ → YZ for any Z
3. Transitivity: if X → Y and Y → Z, then X → Z

I understand the augmentation and transitivity for example if we had such schema:

SOME_SCHEMA(a, b, c, d)

with such functional dependencies:

1. a → b
2. b → c

By using augmentation we could get ac → bc or by using transitivity we could get a → c and much more, however I am not sure how to infer more functional dependencies using reflexivity axiom? What does it really means that some attribute is a subset of some other attribute?

Could you show me an example using my schema or creating your own, please?

Thank you very much in advance!

P.S. Not sure what tag I should use for this question, feel free to change it and remove this line.

As you know there are three Armostrong's Axioms for inferring all the functional dependencies on a relational database. (X, Y and Z are set of attributes)

1. Reflexivity: If X ⊆ Y, then Y → X
2. Augmentation: If X → Y, then XZ → YZ for any Z
3. Transitivity: if X → Y and Y → Z, then X → Z

I understand the augmentation and transitivity for example if we had such schema:

SOME_SCHEMA(a, b, c, d)

with such functional dependencies:

1. a → b
2. b → c

By using augmentation we could get ac → bc or by using transitivity we could get a → c and much more, however I am not sure how to infer more functional dependencies using reflexivity axiom? What does it really means that some attribute is a subset of some other attribute?

Could you show me an example using my schema or creating your own, please?

Thank you in advance!

P.S. Not sure what tag I should use for this question, feel free to change it and remove this line.