Re: Nested Sets vs. Nested Intervals

amado.alves_at_netcabo.pt wrote:
> In the Dot language (Graphviz from AT&T):
>
> digraph {
> Employees -> x1
> Employees -> x2
> Employees -> x3
> Name -> x4
> Name -> x5
> Name -> x6
> Dept -> x7
> Dept -> x8
> Dept -> x9
> Salary -> x10
> Salary -> x11
> Salary -> x12
> Departments -> x13
> Departments -> x14
> Deptno -> x15
> Deptno -> x16
> Name -> x17
> Name -> x18
> x1 -> x4 -> Smith
> x1 -> x7 -> x13
> x1 -> x10 -> 1000
> x2 -> x5 -> Scott
> x2 -> x8 -> x14
> x2 -> x11 -> 2000
> x3 -> x6 -> King
> x3 -> x9 -> x14
> x3 -> x12 -> 3000
> x13 -> x15 -> 1
> x13 -> x17 -> Accounting
> x14 -> x16 -> 2
> x14 -> x18 -> Manufacturing
> }

I'm sorry, I started to draw the graph until I saw  x1 -> x4 -> Smith
What is this -- an abbreviation for 2 adjacent edges? x1 -> x4
x4 -> Smith
Or some kind of labeled edge?

> Note this is a canonical, literal translation of the given relational
> database. Modelling the semantic domain directly on Mneson would
> simplify things. For example the Deptno is probably not necessary
> semantically but just a requirement of the relational model for a key,
> or for the connection (join), or both. Mneson does not need keys. A
> distinct entity is a distinct vertex. Connected entities simply share a
> topology.

I agree, you can remove the Deptno -- I will be able to understand the model without it. Received on Fri Nov 11 2005 - 02:42:38 CET