Relation algebra

In mathematics and abstract algebra, a relation algebra is a residuated Boolean algebra expanded with an involution called converse, a unary operation. The motivating example of a relation algebra is the algebra 2^X² of all binary relations on a set X, that is, subsets of the cartesian square X², with R•S interpreted as the usual composition of binary relations R and S, and with the converse of R interpreted as the inverse relation.