and also finite groups because many regular two-graphs have interesting automorphism groups.

A two-graph is not a graph and should not be confused with other objects called 2-graphs in graph theory, such as 2-regular graphs.

Examples

On the set of vertices {1,...,6} the following collection of unordered triples is a two-graph:
:123 124 135 146 156 236 245 256 345 346This