 
Summary: Equalisers of frames in constructive set theory
DRAFT
Peter Aczel petera@cs:man:ac:uk
Departments of Mathematics and Computer Science
Manchester University
January 18, 2005
Contents
1 Introduction 1
2 MVsetbases 2
3 The setpresentation of ^
A 3
4 Proof of Lemma 1 4
1 Introduction
In a recent note Erik Palmgren has shown that the category of setpresented
formal topologies has coequalisers in a suÆciently strong version of Martin
Lof's type theory.
Here we want to get a version of Palmgren's result in a suÆciently strong
version of constructive set theory. We prefer to work with the category of
setpresented class frames, a category that is equivalent to the opposite of
the category of setpresented formal topologies. So we want to show that the
