category theory Category theory is a general theory of mathematical structures and their relations. It was introduced by Samuel Eilenberg and Saunders Mac Lane in the middle of the 20th century in their foundational work on algebraic topology. Category theory ...

, a branch of

mathematics Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...

, a pulation square (also called a Doolittle diagram) is a diagram that is simultaneously a pullback square and a pushout square. It is a self-dual concept.

References

* Adámek, Jiří, Herrlich, Horst, & Strecker, George E. (1990)
''Abstract and Concrete Categories''
(4.2MB PDF). Originally publ. John Wiley & Sons. . (now free on-line edition) *Herrlich, Horst, & Strecker, George E., ''Category Theory'', Heldermann Verlag (2007). Category theory {{categorytheory-stub