Definition 0.1. Let 𝔾B and 𝔾B* be two groupoids whose object spaces are Borel. An
algebraic morphism from 𝔾B to 𝔾B* is defined as a left action of 𝔾B on 𝔾B* which commutes
with the multiplication on 𝔾B. Such an algebraic morphism between Borel groupoids is said
to be a Borel morphism if the action of 𝔾B on 𝔾B* is Borel (viz. ref. [1])
References
[1] M.R. Buneci. 2006., Groupoid C*-Algebras., Surveys in Mathematics and its
Applications, Volume 1: 71–98.
