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Chapter 2: Adjacency List Model > 2.2 The Simple Adjacency List Model Is Not No... - Pg. 28

2.2 The Simple Adjacency List Model Is Not Normalized 13 among nodes. This is not a flaw in the adjacency list model per se, but this is how most programmers I have seen actually program the adjacency list model. In fairness, one reason for not having all of the needed constraints is that most SQL products did not have such features until their later releases. The constraints that should be used are complicated and we will get to them after this history lesson. I am first going to attack a "straw man," which shows up more than it should in actual SQL programming, and then make corrections to that initial adjacency list model schema. Finally, I want to show some actual flaws in the adjacency list model after it has been corrected. 2.2 The Simple Adjacency List Model Is Not Normalized There is a horrible truth about the simple adjacency list model that nobody noticed. It is not a normalized schema. A boss is not an attribute of an employee any more than a book is an attribute of an author; subordination and authorship are relationships. The classic normal forms are only part of normalization. The short