Consider the following relation schema: WORK(Operator, Item-Made, Machine, Date)

Question

Consider the following relation schema: WORK(Operator, Item-Made, Machine, Date). (1) Formulate the following constraints on this relation schema as functional dependencies: (a) an operator can work on only one machine on the each Item-Made(e.g., skirt, hat)must be made on the same machine. (2) Assume that the following functional dependencies on relation schema WORK: {Operator, Machine} rightarrow {Item-Made, Date), Item-Made rightarrow Machine are given.(Do not consider the F.D.s in the above Question (1)). Is relation schema WORK in 3NF with respect to this given set of F.D.s? Why?

Explanation / Answer

1.Functional Dependencies are as follows:

a.(Operator, date) -----> (Machine)
b.(Machine)---------->(list of items_made)

2.3NF needs that all the non key attributes should only depend on the key. In this case the key is
{Operator, Machine} but the other non key attribute item_made depends on "date" along with the key attribute and hence
the WORK schema condidering the FDs in the 2nd part of the question is not 3NF.

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