Relations are Sets of Points
The N-tuples of a Relation R(x,y,z) have values in the Direct Product space XxYxZ of its participating component domains. In other words, the value of any Relation is a subset of points in the direct product space of its components:
- Range(Relation(x,y,z)) ?
Range(x) x Range(y) x Range(z)
An N-ary relation is a set of N-tuples, each of which specifies or contains one instance of each of the participating entity types.
- Binary relations(N=2) are common.
- Ternary(N = 3) and higher relations are rare (Examples?)