  In [Incer Romeo, I. X., \textit{The Algebra of Contracts}. Ph.D. Thesis, UC
Berkeley (2022)] an algebraic perspective on assume-guarantee contracts is
proposed. This proposal relies heavily on a construction involving Boolean
algebras. However, the structures thus proposed lack a clearly prescribed set
of basic operations, necessary if we want to see them as a class of algebras
(in the sense of Universal Algebra). In this article, by prescribing a suitable
set of basic operations on contracts, we manage to describe these algebras as
(a generating set of members of) well-known varieties.
