This talk was given on June 28, 2009 at the Bio-Ontologies SIG as part of ISMB/ECCB 2009. You can download the paper this presentation is about from http://hdl.handle.net/10101/npre.2009.3286.1. More information on the ISMB conference is available at http://www.iscb.org/ismbeccb2009/ and http://friendfeed.com/ismbeccb2009