Re: Nested Sets vs. Nested Intervals

From: <amado.alves_at_netcabo.pt>
Date: 10 Nov 2005 17:10:19 -0800
Message-ID: <1131671419.912242.239800@z14g2000cwz.googlegroups.com>

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
}

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. Received on Thu Nov 10 2005 - 19:10:19 CST