This document should be of interest to those working in combinatorial or statistical design theory, as well as those interested in the development of standard electronic formats for mathematical objects.

We at *DesignTheory.org* are in the process of developing a
web-based Design Theory Resource Server
(http://designtheory.orgDTRS) for combinatorial and statistical
design theory. One critical element is our *External
Representation of Designs* which will be used to store designs and their
combinatorial, group theoretical and statistical properties in a
standard platform-independent manner (*external* means external to
any software). This will allow for the straightforward exchange of
designs and their properties between various computer systems, including
databases and web servers, and combinatorial, group theoretical and
statistical packages. The external representation will also be used for
outside submissions to our design database.

We have concentrated our initial development effort in the area of block
designs, and in this document we present our standard for the
*External Representation of Block Designs*. We shall give a full
explanation and provide examples. We have tried to make the document
readable by non-experts, since we don't expect everyone to be an expert
in all the areas covered.