  We study internal structures in regular categories using monoidal methods.
Groupoids in a regular Goursat category can equivalently be described as
special dagger Frobenius monoids in its monoidal category of relations.
Similarly, connectors can equivalently be described as Frobenius structures
with a ternary multiplication. We study such ternary Frobenius structures and
the relationship to binary ones, generalising that between connectors and
groupoids.
