Abstract
The relational model as such has its origins in two landmark papers by Codd:
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- 1.
However, this paper isn’t concerned so much with 2NF and 3NF per se as it is with the idea that relations can represent anything that other data structures—hierarchies, networks, etc.—can. It does discuss 2NF and 3NF very briefly, but its coverage of those topics is essentially limited to giving a single fairly informal example in each case.
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In fact Codd’s contribution to that workshop references Heath’s, while Heath’s in turn references Codd’s as yet unpublished 1972 paper on 2NF and 3NF. By the way, it’s pertinent to point out that Heath’s paper certainly appeared before Codd’s 1974 paper that defined what’s now called BCNF (see Chapter 5 for further elaboration of this point).
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Using “X ⊆ Y” to represent the IND “X is included in Y,” the rules in question can be stated as follows:
1. X ⊆ X.
2. If XY ⊆ ZW, then X ⊆ Z and Y ⊆ W.
3. If X ⊆ Y and Y ⊆ Z, then X ⊆ Z.
Note that these rules are obviously valid if “⊆” is replaced by “=” (i.e., if the INDs are in fact EQDs).
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© 2019 C. J. Date
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Date, C.J. (2019). Historical Notes. In: Database Design and Relational Theory. Apress, Berkeley, CA. https://doi.org/10.1007/978-1-4842-5540-7_21
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DOI: https://doi.org/10.1007/978-1-4842-5540-7_21
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