Subject: question for the topology list
Date: Mon, 11 Mar 2002 16:36:21 +0000
From: james cruickshank <james.cruickshank@nuigalway.ie>

I have a question for the topology list:

I have recently been thinking about the following category in connection
with knot invariants: The objects are groups. A morphism G_1 --> G_2
is diagram G_1 --> H <-- G_2. Two morphisms are composed
by taking pushout. I am sure that I have seen this category mentioned
somewhere but I can't remember where. Can anyone supply a reference
that would contain information about this category?

Thanks

Jim Cruickshank.