Subject: question to topology list re category
Date: Wed, 13 Mar 2002 09:07:53 -0600
From: David Yetter
Joan Birman forwarded to me the question posed by James Cruickshank
to the topology list.
I have not seen the specific category you asked about before, but in
general if one has a
category C with (chosen) pushouts for all pairs of maps with a common
source, the category
with diagrams of the form X----> M <------Y as arrows, and composition
given by pushout
is called the category of cospans in C.
(For some reason it has been more common among categorists to
consider the dual notion--
the category of spans in a category with pullbacks.)
Best Thoughts,
David Yetter