Database Reference
In-Depth Information
5.2.1 Transitive dependence
Z is transitively dependent on X when X determines Y and Y determines Z.
Transitive dependence thus describes that Z is indirectly dependent on X through its
relationship with Y.
Here is the transitivity rule restated:
Given X Y
Given Y Z
Then X Z
5.2.2 The Reflexive Rule
If X is a composite, composed of A and B, then X A and X B.
X = Name, City. Then we are saying that X Name and X City.
The rule, which seems quite obvious, says if I give you the combination <Sachin, Amrit-
sar>, what is this person's Name? What is this person's City?
5.2.3 The Augmentation Rule
If X Y, then XZ Y. You might call this rule, “more information is not really needed,
but it doesn't hurt.”
5.2.4 The Decomposition Rule
The decomposition rule says that if it is given that X YZ (that is, X defines both
Y and Z), then X Y and X Z.
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