Collagories: Relation-algebraic reasoning for gluing constructions

The relation-algebraic approach to graph transformation has previously been formalised in the context of complete distributive allegories. Careful analysis reveals that the zero laws postulated for distributive allegories were never used, and that completeness was most importantly used for the difunctional closures necessary for a relation-algebraic characterisation of pushouts.We therefore define collagories essentially as “distributive …