You are right. It is called slice categories. Michael Barr

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From john@cs.keele.ac.uk Tue Jul 1 04:09:41 1997 Received: from gabriel.cc.keele.ac.uk (gabriel.cc.keele.ac.uk [160.5.20.2]) by triples.math.mcgill.ca (8.6.8/8.6.6) with ESMTP id EAA08244 for <barr@triples.math.mcgill.ca>; Tue, 1 Jul 1997 04:09:39 -0400 Received: from nina.cs.keele.ac.uk by gabriel with SMTP (PP); Tue, 1 Jul 1997 09:17:11 +0100 From: "John G. Stell" <john@cs.keele.ac.uk> Date: Tue, 1 Jul 1997 09:14:56 +0100 Message-Id: <6826.199707010814@nina.cs.keele.ac.uk> To: barr@triples.math.mcgill.ca Subject: comma categories Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-MD5: P4mFcjNdTLEYzYzmOK7OUw== Status: R

Not that I am blowing my own horn (but why not), you will find something about comma categories in Barr & Wells, Category Theory for Computing Science. But no, I know of no other research along those lines.

Michael Barr

Pehaps it would be helpful to the original enquirer to say where it can be found. I am unable to find it in the index of either edition. John Stell