A paper on double categories

The following paper, in press in a volume dedicated to B. Banaschewski, is downloadable online: M. Grandis - R. Paré, Span and cospan representations of weak double categories, Categ. Gen. Algebr. Struct. Appl., Vol. 6 n. 5, in press Published online (18 Nov 2016) at: http://www.cgasa.ir/? _action=press&issue=-1&_is=Articles%20in%20Press Abstract. We prove that many important weak double categories can be `represented' by spans, using the basic higher limit of the theory: the tabulator. Dually, representations by cospans via cotabulators are also frequent. Marco Grandis and Bob Paré [For admin and other information see: http://www.mta.ca/~cat-dist/ ]