In confirming that the algebraic calculations of
[Markus Rost, On the dimension of a composition algebra, Documenta Mathematica 1 (1996) 209–214]
do actually work in any ``tensor category' as claimed therein, I found with some care that they even work in a braided monoidal additive category. The ACS talk by John Baez on 23 January 2003 alerted me to the work of Rost and his students Dominik Boos and Susanne Maurer. It was the topic of my talk last Friday in Newcastle at the Workshop on Diagrammatic Reasoning in Higher Education.