Definition 5.1 (Cartesian Product)
A × B = { (x,y)  x A and y B }
are sets. The set of all ntuples with , 1 i n, is denoted by
We write:
= { (

, 1 i n }
Examples:
Definition 5.2 (Relation)
If (x,y) R we say x is Rrelated to y.
To express that R is a relation from A to B we write R: A B
Shorthand: (x,y) R xRy
Examples:
A relation C can now be defined as a list of pairs (x,y) where x is a supplier and y is a product.
C = { (S1, P1) , (S1, P3), (S2, P2), (S2, P3) }
Relation in tabular form:
+++++   P1  P2  P3  +++++ S1  1  0  1  +++++ S2  0  1  1  +++++
A graphically representation of the relation board
Last modified: 27/July/98 (12:14)