co-universal square, pull-back square, in a category
Here (the notation is also used) is the fibred product of the objects and , which is associated with
and and are the canonical projections. The diagram
is a Cartesian square if and only if it is commutative and if for any pair of morphisms , such that there exists a unique morphism which satisfies the conditions , .
|||I. Bucur, A. Deleanu, "Introduction to the theory of categories and functors" , Wiley (1968)|
Cartesian square. O.A. Ivanova (originator), Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Cartesian_square&oldid=13918