^^Relazione binaria tra 2 insiemi; in un insieme.

Relazione binaria tra 2 insiemi X e Y
un insieme di coppie ordinate (x,y)  x∈X  y∈Y
un sottoinsieme del prodotto cartesiano XxY
Relazione binaria in/su un insieme X
un insieme di coppie ordinate (x,y)  x,y∈X
un sottoinsieme del prodotto cartesiano XxX

Binary relation over a set X

≡  Homogeneous relation  ≡  endorelation,

Es

An example of a homogeneous relation is the relation of kinship, where the relation is over people.

 

Teo: A relation over a set may be identified with a directed graph

a relation XRX is identified with the directed graph where

It is called the adjacency relation of the graph.

 

If the relation is symmetric, with an undirected graph.