Dear Category Theory gurus, Is there any literature in which MacLane's "super comma category" (Cat./.C) of all small diagrams in a category C is studied in details? Actually I work in its covariant form, where a morphism from a diagram D:X->C to G:Y->C is a pair (e,F) consisting of a functor F:X->Y and a natural transformation e:D->GF. For example, is it known that the embedding of an ordinary comma category Cat/C into Cat./.C preserves colimits? Also there exists a monad (Cat./.-, d, m) on CAT, where d_C takes each C-object X to a discrete diagram {X}, and m represents "drawing" a diagram of diagrams as a diagram. Is its Eilenberg-Moore category isomorphic to some "familiar" construction? Thanks, Serge. [For admin and other information see: http://www.mta.ca/~cat-dist/ ]