Full Idea
While in general a relation is taken to be a set of ordered pairs <u, v> = {{u}, {u, v}}, and hence a set of sets of sets, in special cases a relation can be represented by a set of sets.
Gist of Idea
A relation is either a set of sets of sets, or a set of sets
Source
JP Burgess / G Rosen (A Subject with No Object [1997], II.C.1.a)
Book Reference
Burgess,J/Rosen,G: 'A Subject with No Object' [OUP 1997], p.150
A Reaction
[See book for their examples, which are <, symmetric, and arbitrary] The fact that a relation (or anything else) can be represented in a certain way should never ever be taken to mean that you now know what the thing IS.